Intrusion Detection

Systems and Subsystems

Technical Information for

NRC Licensees 

Office of Nuclear Security and Incident Response 

NUREG-1959
Intrusion Detection

Systems and Subsystems

Technical Information for

NRC Licensees 

Manuscript Completed: November 2010 

Date Published: March 2011

Office of Nuclear Security and Incident Response 

NUREG-1959
 iii 

ABSTRACT 

This report provides information relative to designing, installing, testing, maintaining, and 

monitoring intrusion detection systems (IDSs) and subsystems used for the protection of 

facilities licensed by the U.S. Nuclear Regulatory Commission. It contains information on the 

application, use, function, installation, maintenance, and testing parameters for internal and 

external IDSs and subsystems, including information on communication media, assessment 

procedures, and monitoring. This information is intended to assist licensees in designing, 

installing, employing, and maintaining IDSs at their facilities.
 v 

CONTENTS

Abstract ....................................................................................................................................... iii

Contents ........................................................................................................................................ v

List of Figures ............................................................................................................................. vii

List of Tables ................................................................................................................................ ix

1. Introduction ......................................................................................................................... 1-1

2. Intrusion Detection Systems ............................................................................................... 2-1

2.1 Overview .................................................................................................................... 2-1

2.2 Intrusion Detection Equipment ................................................................................... 2-1

2.3 System Considerations .............................................................................................. 2-3

3. Exterior Detection Sensors ................................................................................................. 3-1

3.1 Microwave Sensors .................................................................................................... 3-1

3.2 Electric Field Sensors ............................................................................................... 3-10

3.3 Ported Coaxial Cable Systems ................................................................................. 3-18

3.4 Active Infrared Sensors ............................................................................................ 3-26

3.5 Taut Wire Sensors .................................................................................................... 3-34

3.6 Fence Disturbance Sensors ..................................................................................... 3-42

4. Interior Intrusion Detection Sensors ................................................................................... 4-1

4.1 Balanced Magnetic Switch ......................................................................................... 4-1

4.2 Interior Microwave Sensors ........................................................................................ 4-7

4.3 Passive Infrared ....................................................................................................... 4-15

4.4 Proximity Sensors .................................................................................................... 4-24

4.5 Dual-Technology Sensors ........................................................................................ 4-33

4.6 Video Motion Detection ............................................................................................ 4-39

5. Waterborne Sensors ........................................................................................................... 5-1

5.1 Waterborne Sensor Systems ..................................................................................... 5-1

6. Video Assessment .............................................................................................................. 6-1

6.1 Video Assessment Systems ....................................................................................... 6-1

6.2 Cameras ..................................................................................................................... 6-5

6.3 Digital Video Recorders ............................................................................................ 6-18

6.4 Lighting ..................................................................................................................... 6-23

6.5 Video Assessment System Testing .......................................................................... 6-45

6.6 Maintenance ............................................................................................................. 6-55

7. Owner-controlled Area Surveillance ................................................................................... 7-1

7.1 Overview of Concepts and Definitions ....................................................................... 7-1

7.2 Binoculars................................................................................................................... 7-2

7.3 Spotting Scopes ......................................................................................................... 7-4

7.4 Night Vision Devices .................................................................................................. 7-5

7.5 Thermal Imager Equipment ........................................................................................ 7-6

7.6 Enhanced Night Vision (Fusion) ................................................................................. 7-7

8. Alarm Communication and Display ..................................................................................... 8-1

8.1 Principles of Operation ............................................................................................... 8-1

8.2 General Guidance for Alarm Communication and Display Systems .......................... 8-1

8.3 Types of Alarm Communication and Display Systems Available ............................... 8-9

8.4 Sources of Nuisance Alarms ...................................................................................... 8-9

8.5 Installation Criteria ...................................................................................................... 8-9
 vi 

8.6 Testing........................................................................................................................ 8-9

8.7 Maintenance ............................................................................................................. 8-12

9. Emergency and backup Power ........................................................................................... 9-1

9.1 Principles of Operation ............................................................................................... 9-1

9.2 Types of Emergency and Backup Power Supplies .................................................... 9-2

9.3 Installation Criteria ...................................................................................................... 9-3

9.4 Testing........................................................................................................................ 9-3

9.5 Maintenance ............................................................................................................... 9-7
 vii 

LIST OF FIGURES

Figure 1: Photo depicting the application of microwave sensors within a PIDAS ..................... 3-1 

Figure 2: Diagram depicting the detection zone of a typical bistatic microwave ....................... 3-2 

Figure 3: Diagram depecting the detection zone of a typical monostatic microwave. ............... 3-2 

Figure 4: Examples of possible microwave sensor layouts. ..................................................... 3-4 

Figure 5: Example of a corner setup of microwave sensors that provides overlap ................... 3-5 

Figure 6: Possibility of using the microwave structure to jump over its own detection zone ..... 3-6 

Figure 7: An example of stacked microwave sensors ............................................................... 3-7 

Figure 8: An aluminum sphere used for crawl testing the mocrowave detection system.......... 3-8 

Figure 9: Testing microwave sensors with an aluminum sphere. ............................................. 3-9 

Figure 10: Example of an electric field sensor installed in a test environment. ....................... 3-11 

Figure 11: A cross-section of an electric field sensor’s zone of detection............................... 3-11 

Figure 12: Various configurations for electric field sensors. ................................................... 3-12 

Figure 13: Sources of nuisance alarms for electric field sensors ............................................ 3-13 

Figure 14: Main components of an electric field sensor installation. ....................................... 3-15 

Figure 15: An example of the crawl-test procedure. ............................................................... 3-17 

Figure 16: An illustration of the covert zone of detection for a ported coax sensor. ............... 3-19 

Figure 17: A typical installation and detection envelope for a ported coax sensor. ................ 3-19 

Figure 18: Examples of ported coax cables. ........................................................................... 3-20 

Figure 19: Sources of nuisance alarms for ported coaxial cable detection systems ............... 3-21 

Figure 20: Typical ported coax cable system installation. ....................................................... 3-23 

Figure 21: Effects of metal objects or utilities located near a ported coax system. ................. 3-24 

Figure 22: Ideal test mehtod for a ported coaxial system ....................................................... 3-25 

Figure 23: Multibeam active infrared sensor columns ............................................................ 3-27 

Figure 24: Active Infrared sensors vary in beam configuration ............................................... 3-28 

Figure 25: Active infrared sector intersection methods. .......................................................... 3-31 

Figure 26: A freestanding taut wire installation for environmental testing. .............................. 3-35 

Figure 27: A taut wire sensor system installed on an existing fence....................................... 3-36 

Figure 28 Taut wire push test ................................................................................................. 3-36 

Figure 29: Examples of sources of nuisance alarms for taut wire fencing. ............................. 3-38 

Figure 30: Measuring deflection on a taut wire sensor ........................................................... 3-41 

Figure 31: Diagram illustrating the deflection caused by climbing on chain-link fence fabric. 3-43 

Figure 32: Typical installation of strain-sensitive cable. .......................................................... 3-45 

Figure 33: Example of security fence wire ties. ...................................................................... 3-48 

Figure 34: An example of a fence-cut simulation tool in use. ................................................. 3-50 

Figure 35: Test climbing the fence from the outer (unprotected) side..................................... 3-51 

Figure 36: An example of the application of a magnetic switch for door protection. ................. 4-1 

Figure 37: A schematic of a simple versus balanced magnetic switch. .................................... 4-2 

Figure 38: Demonstration of introducing an external magnetic field to a BMS ......................... 4-6 

Figure 39: A common interior microwave antenna propagation pattern. .................................. 4-7 

Figure 40: Examples of different microwave antenna propagation patterns ............................. 4-8 

Figure 41: Example of a microwave sensor triggering a nuisance alarm ................................. 4-9 

Figure 42: Differences in detection patterns for microwave sensors. ..................................... 4-11 

Figure 43: Recommended walk teste for performance testing a microwave sensor. .............. 4-14 

Figure 44: Detection pattern for a typical installation of a PIR sensor. ................................... 4-15 

Figure 45: Example of a PIR sensor's subdivided detection pattern. ...................................... 4-16 
 viii 

Figure 46: An example of a curtain PIR application. ............................................................... 4-17 

Figure 47: Illustration of the detection pattern of a ceiling-mounted PIR sensor .................... 4-17 

Figure 48: Recommended walk tests for the performance testing of a PIR sensor. ............... 4-22 

Figure 49: A typical PIR detection pattern derived from walk tests towards the sensor. ........ 4-23 

Figure 50: Example of portable, high-value items. .................................................................. 4-27 

Figure 51: Example of a capacitance sensor installation. ....................................................... 4-28 

Figure 52: Example of a pressure mat intrusion detection sensor. ......................................... 4-28 

Figure 53: Strain sensor concept to detect person on stairs. .................................................. 4-29 

Figure 54: Example of a mat sensor near door. ...................................................................... 4-30 

Figure 55: Dual-technology sensor (PIR sensor and a microwave sensor). ........................... 4-34 

Figure 56: Walk test areas in a room covered by a dual-technology PIR-microwave sensor. 4-39 

Figure 57: An example of a fiber-optic grid covering a water intake channel. .......................... 5-1 

Figure 58: Potential degradation of undewater fiber-optic grid sensors. ................................... 5-2 

Figure 59: Diagram of an analog video system. ....................................................................... 6-2 

Figure 60: Diagram of a network-based digital video system. .................................................. 6-3 

Figure 61: Examples of laboratory black and white and color camera resolution charts. ......... 6-6 

Figure 62: Example of a resolution chart test setup. ................................................................. 6-7 

Figure 63: Examples of field resolution charts (Rotakin at right). ............................................. 6-7 

Figure 64: Example of video image showing detection. ............................................................ 6-8 

Figure 65: Example of video image showing classification. ...................................................... 6-8 

Figure 66: Example of video image showing identification. ...................................................... 6-8 

Figure 67: Images of high- and low-contrast scenes. ............................................................. 6-13 

Figure 68: Camera sensitivity at light level. ............................................................................ 6-14 

Figure 69: Video motion detection image showing intruder tracking. ..................................... 6-22 

Figure 70: Example of lighting with hot spots, dark areas, and dirt ground cover................... 6-25 

Figure 71: Improved assessment visibility with even lighting and regular ground surface ...... 6-25 

Figure 72: Contrast differences created by outdoor lighting. .................................................. 6-27 

Figure 73: An example of a perimeter with controlled lighting. ............................................... 6-28 

Figure 74: Examples of light-to-dark ratios for camera assessment. ...................................... 6-31 

Figure 75: Recommended height differences between exterior lighting and cameras. .......... 6-36 

Figure 76: An example output from an illumination modeling software system. ..................... 6-37 

Figure 77: Checking light levels using a light meter within a perimeter isolation zone ........... 6-40 

Figure 78: Preparation for measuring perimeter lighting illumination. ..................................... 6-41 

Figure 79: Points at which to measure light readings. ............................................................ 6-43 

Figure 80: Challenges of surveillling a large area such as an owner-controlled area ............... 7-1 

Figure 81 The use of enhanced night vision devices for fusion technology .............................. 7-8 

Figure 82: An optimal arrangement of AC&D monitors. ............................................................ 8-4 

Figure 83: Using fault trees to analze system events ............................................................. 8-10 

Figure 84: Symbols used in the graphical representation of a fault tree. ................................ 8-11 

Figure 85: Use of emergency and/or backup power supplies in the event of a loss of power. . 9-1 
 ix 

LIST OF TABLES 

Table 1: Assessment Type and Required Pixels ...................................................................... 6-9 

Table 2 Imager Formats, Converting Inches to Millimeters ................................................... 6-12 

Table 3: Image Sizes for Common Intermediate Format Image Sizes ................................... 6-23 

Table 4: Relative Illumination Levels under Various Lighting Conditions ............................... 6-30 

Table 5: Typical Reflectance for Various Common Surfaces ................................................. 6-30 

Table 6: Ranges for Average Illumination Values That Will Give 4:1 Light-to-Dark Ratios ..... 6-32 

Table 7: Characteristics of Seven Common Types of Bulbs ................................................... 6-39 

Table 8: Perimeter Light Measurements ................................................................................. 6-44 

Table 9: Operations Testing Matrix ......................................................................................... 8-12 

Table 10: Typical Lead-Acid Battery/Cell Surveillance and Tests ............................................ 9-6 
1-1 

1. INTRODUCTION 

This report provides information about designing, installing, testing, maintaining, and monitoring 

intrusion detection systems (IDSs) and subsystems used for the protection of facilities licensed 

by the U.S. Nuclear Regulatory Commission (NRC). Title 10 of the Code of Federal 

Regulations Part 73, “Physical Protection of Plants and Materials,” addresses the NRC’s 

requirements for the physical protection of nuclear power reactor facilities, independent spent 

fuel storage facilities, fuel cycle facilities, strategic special nuclear materials, and special nuclear 

material of moderate and low strategic significance. The specific requirements for physical 

protection programs at NRC-licensed facilities are determined by the type of NRC licensee and 

the special nuclear material authorized to be possessed by that licensee. 

The use of IDSs at NRC-licensed facilities is one component of a physical protection program, 

the purpose of which is to ensure that only authorized personnel gain access to areas 

containing nuclear materials and that the use of nuclear materials does not endanger the public 

health and safety. 

It is important to note that the effectiveness of a physical protection program depends on the 

coordination and integration of all the various components of that program, from equipment, to 

policies, to personnel, as well as the ability of the licensee to monitor and maintain these 

components to ensure they operate as intended. The use of IDSs is just one component of the 

overall physical protection program. Therefore, each licensee should design, install, and 

maintain an IDS that complements the needs and implementation of the other components of 

the physical protection program. 

The following sections of this report provide information pertinent to the application, use, 

function, installation, maintenance, and testing parameters for internal and external IDSs and 

subsystems, including information on alarm communication media, assessment technology, and 

monitoring. The information is intended to assist licensees in designing, installing, employing, 

and maintaining IDSs at their facilities. When applying this information, it is important to confirm 

that site-specific conditions are analyzed and accounted for and that manufacturer 

recommendations for system application, installation, maintenance, and testing are followed to 

ensure the system capabilities are consistent with the physical protection program goals and 

that the systems are capable of performing their intended functions. 

 2-1 

2. INTRUSION DETECTION SYSTEMS 

2.1 Overview

Intrusion detection and assessment systems are an integral part of any physical protection 

system. Detection and assessment provide a basis for the initiation of an effective security 

response. Intrusion detection systems (IDSs) should be designed to facilitate the detection of 

attempted and actual unauthorized entry into designated areas and should complement the 

security response by providing the security force with prompt notification of the detected activity 

from which an assessment can be made and a response initiated. The method(s) of detection 

and assessment selected for implementation should be robust and be capable of providing the 

highest level of protection for the specific application. In the design of the detection and 

assessment aspects of a physical protection system, various methodologies should be 

incorporated to provide a fully integrated detection capability. The integration of various 

detection and assessment methodologies not only contributes to a superior detection and 

assessment capability, but also provides multiple overlapping layers that support each other if 

one method fails. 

2.2 Intrusion Detection Equipment

2.2.1 Premise Control Unit 

A premise control unit (PCU) is a device that receives changes of alarm status from sensors 

and transmits an alarm condition to the alarm monitoring station. The PCU also allows 

authorized personnel to change the alarm zone status of the alarm zone. 

To be useful, an intrusion alarm system should have the capability to restrict status changes to 

only those who possess proper authority such as alarm system administrators or alarm station 

operators. A system may restrict access to performing system functions in any number of ways, 

often with keys or codes used at the PCU or a remote PCU near an entry. High-security alarms 

may require multiple codes, a fingerprint, badge, hand-geometry, retinal scan, encrypted 

response generator, and/or other means that are deemed sufficiently secure for the purpose. 

To function as intended, the PCU must be located within the secured area to protect it from 

unauthorized access. The alarm status is normally delayed (for no more than 30 seconds) to 

allow the entrance authorization process to be completed. Like the sensors, the PCU requires a 

primary power source for operation and should be connected to an emergency power source to 

remain operable during the loss of primary power. The PCU should be equipped with a tamper 

alarm to detect attempts at unauthorized manipulation. All changes in status of the alarm zone 

must be transmitted to the alarm monitoring stations. Examples of reportable status include but 

are not limited to access/secure, tamper, loss of power, improper access code or procedure, 

test or maintenance mode, and masked sensors. PCUs can be configured with duress 

capabilities, which will allow personnel to surreptitiously notify the alarm monitoring station of a 

compromised situation. 
 2-2 

2.2.2 Transmission and Annunciation 

To ensure transmission line security, when the transmission line leaves the facility and traverses 

an uncontrolled area, Class I or Class II line supervision should be used. 

2.2.2.1 Class I 

Class I transmission line security is the security achieved through the use of a data encryption 

system or an algorithm based on the cipher feedback or cipher block chaining mode of 

encryption. To ensure Class I transmission line security, the data encryption system used must 

be certified by the National Institute of Standards and Technology or another independent 

testing laboratory. 

2.2.2.2 Class II 

Class II transmission line security refers to systems in which the transmission is based on 

pseudo random-generated tones or digital encoding using an interrogation and response 

scheme throughout the entire communication, or Underwriters Laboratories Class AA line 

supervision. The signal must not repeat itself within a minimum 6-month period. Class II 

transmission line security must also be protected against compromise using resistance, voltage, 

current, or signal substitution techniques. 

Note: Direct current (dc) line supervision should not be used because it is highly susceptible to 

manipulation or substitution to circumvent valid alarm annunciation. Additional information on 

alarm communication and display (AC&D) can be found in Section 8 of this report. 

2.2.3 Intrusion Detection System Cabling 

Cabling designs that combine signal transmission lines and power source cabling into one of the 

two alarm monitoring stations or one common area before they reach the alarm monitoring 

stations should be avoided. Facilities should, to the extent practicable, ensure that the cabling 

(signal transmission and power) to each alarm station is sufficiently separated and not 

accessible to external manipulation. The separation and nonaccessibility of cabling provide a 

level of assurance that at least one alarm station will maintain the capability to perform required 

alarm station functions if the cabling is subject to an occurrence that results in the loss of 

functionality within the other alarm station. Key considerations in the design and installation of 

alarm system cabling are the prevention of unauthorized and external manipulation and 

minimization of the exposure to environmental conditions. It is important to identify and 

evaluate intrusion detection and assessment system cabling that may be vulnerable to 

disruption by external manipulation (e.g. adversarial action) and consider further protective 

measures such as hardening or periodic surveillance. 

The cabling between the sensors and the PCU should be dedicated to the intrusion detection 

equipment (IDE) for which it provides service and should comply with national and local code 

standards. Cabling should be installed in metal conduit between the alarmed area(s) (i.e., 

controlled access area (CAA), vital area (VA), or material access area (MAA)) PCU and the 

alarm monitoring stations. Exceptions may apply when the cabling is not easily accessible, 

such as when it is run underground, traverses or is within another controlled area, or is 

encrypted with Class I or II encryption. 
 2-3 

2.2.4 Entry Control Systems 

If an entry control system is integrated into an IDS, reports received in the alarm stations from 

the automated entry control system should be subordinate in priority to reports from intrusion 

alarms. Additional information on AC&D appears in Section 8, “Alarm Communication and 

Display,” of this report. 

2.2.5 Power Supplies 

Primary power sources for IDE may be commercial alternating current (ac) or dc power. In the 

event of a failure of primary power, the system should be designed to provide an indication that 

the IDS is operating on secondary, backup, or emergency power sources without causing false 

alarm indications. Section 9 of this report presents additional information on backup and 

emergency power. 

2.2.5.1 Emergency Power 

Emergency power should enable IDE to remain operable during the loss of primary/normal 

power. An emergency power supply should consist of a protected independent power source 

that provides a minimum of 4 hours operating power battery and/or generator power. When 

batteries are used for emergency power, they should be maintained at full charge by automatic 

charging circuits. The manufacturer’s periodic maintenance schedule should be followed and 

results documented. 

2.2.5.2 Power Source and Failure Indication 

A visual (illuminated) and audible indication of power failure should be provided at the PCU of 

the power source in use (ac or dc) and in the alarm monitoring stations. Equipment at the alarm 

stations should indicate a failure in power source, a change in power source, and the location of 

the failure or change. 

2.3 System Considerations

2.3.1 Maintenance Mode 

When an alarm zone is placed in the maintenance mode, this operability status should be 

signaled automatically to the alarm monitoring stations. The signal should appear as an alarm 

or maintenance message at the alarm stations, and the IDS should not be securable while in the 

maintenance mode. The alarm or message should be visible at the alarm stations continually, 

throughout the period of maintenance. A standard operating procedure should be established 

to address appropriate actions when maintenance access is indicated at the panel. A record of 

each maintenance period should be archived electronically in the system or on other electronic 

media, or it may be printed in hard copy, in accordance with site procedures. A self-test feature 

should be limited to one second per occurrence. Section 8 “Alarm Communication and 

Display,” of this report presents additional information on AC&D. 
 2-4 

2.3.2 Shunting or Masking Condition 

Shunting or masking of any alarm zones or sensors should be appropriately logged or recorded 

in the archive. A shunted or masked alarm zone or sensor should be displayed as such at the 

alarm monitoring stations throughout the period that the condition exists. Section 8 “Alarm 

Communication and Display,” of this report presents additional information on AC&D. 

2.3.3 Component Tamper Protection 

IDE components, to include all sensors, control boxes, and junction boxes, should be equipped 

with tamper protection and indication to provide deterrence, delay, and detection of attempted 

unauthorized manipulation. 

2.3.4 System Component Status Changes 

No capability should exist to allow changing the status of the IDE and associated access control 

equipment from a location outside the area for which the equipment is applied. If used, PCUs 

should be located within a secure area that is equipped with intrusion detection capabilities that 

annunciate in the alarm monitoring stations. Only alarm station operators or authorized 

technicians should initiate status changes for IDE and associated access control equipment. 

Operation of the PCU should be restricted by use of a device, password, or procedure that 

verifies the authorization of an individual to make such changes. For applications of increased 

security, status changes for IDE and associated access control equipment may require 

confirmation from an additional system operating authority before the change is allowed to occur 

(e.g., a concurrence action from an alarm station operator confirming the status change initiated 

by the other alarm station operator or authorized technician). 

2.3.5 False and/or Nuisance Alarm 

A false alarm is an alarm generated without apparent cause. False alarms are generally 

attributed to electronic phenomena, whether of the sensor itself or of the electrical infrastructure 

of the sensor system. Alarm signals transmitted in the absence of detected intrusion, or when 

the cause cannot be verified as a nuisance alarm, are false alarms. A nuisance alarm is the 

activation of an alarm sensor by some influence for which the sensor was designed but which is 

not related to an intrusion attempt. To validate detection, all alarms must be assessed and may 

require further investigation to determine the cause. The results of all alarms should be 

documented. The design goal of an intrusion detection system should be to limit false alarms 

and nuisance alarms to a total of not more than one false alarm per zone per day and one 

nuisance alarm per zone per day. A sound maintenance program is often a key factor in 

minimizing the number of false and nuisance alarms an IDS system generates. 

Alarm records should be maintained for effective preventive maintenance. These documented 

records support effective preventive maintenance. These records should include a daily 

nuisance alarm log. A daily nuisance alarm log can aid in the tracking of equipment or sectors 

where maintenance is required. This alarm log should contain an assessment of the cause of 

the alarm and should be referenced by alarm sector, specific location within the sector, and, as 

applicable, by component serial number, which provides unit-specific tracking. The alarm log 

enables problems related to a specific alarm sector to be investigated and identified for 

corrective action. 
 2-5 

2.3.6 Installation, Maintenance, and Testing 

Proper system installation, maintenance, and testing contribute to acceptable system 

performance and minimize its vulnerability to defeat. The defeat vulnerability of the sensor is an 

inherent characteristic of the sensor technology, how it is installed, and how sensors are 

configured within the system. For an effective detection system, intrusion detection sensors 

must be selected and properly installed to: maximize the detection probability, minimize its 

nuisance alarm rate, and minimize its vulnerability to defeat. Intrusion detection and 

assessment systems and components should be installed, maintained, and tested in 

accordance with manufacturers’ specifications which account for system design, application, 

and performance. For IDS systems that are integrated with other components of the physical 

protection system, the specific configuration of all integrated components should be evaluated 

to ensure the system performs its intended function and provides the desired level of protection. 

Prior to installation the planned configuration of perimeter intrusion detection and assessment 

systems, physical barriers at the protected area perimeter (to include any associated nuisance 

barriers), and the isolation zones should be evaluated to ensure that the planned perimeter 

system design will satisfy the detection and assessment goals of the physical protection 

program. After installation, the configuration of these components should be re-evaluated 

based on the zone of detection provided by the IDS when operating to ensure that the IDS 

provides the required coverage and eliminates the potential for unauthorized bypass. The 

configuration of the components of the protected area perimeter (intrusion detection and 

assessment systems, physical barriers and the isolation zones) when combined with the IDS 

zone of detection should account for common defeat methodologies such as walking, crawling, 

running, climbing, jumping and bridging consistent with the design goals of the physical 

protection program. As such, perimeter IDS testing should include all defeat methodologies that 

could be used to defeat the system. With consideration for safety, simulations of certain defeat 

methodologies (e.g. jumping, bridging) during testing may be necessary. 

Intrusion detection and assessment system or component installation, maintenance, and testing 

should be performed only by trained and qualified personnel. All installation, system 

settings/sensitivity levels, maintenance, and testing activities should be documented so that 

they may be used to support system or component troubleshooting and to ensure proper 

performance, maintenance, and testing intervals. 

To ensure that a system or component continues to provide the level of protection intended, 

maintenance, testing, and calibration activities should be performed at intervals consistent with 

manufacturers’ specifications and the operational demand placed on the system or component. 

Most system and component manufacturers have established similar testing criteria, especially 

in the area of testing frequency. The information below reflects general manufacturer 

recommendations regarding intrusion detection and assessment system testing intervals. 

2.3.6.1 Acceptance Testing 

When a sensor is first installed, it must be tested in order to formally “accept” the sensor as a 

part of the physical protection system. Acceptance testing consists of two parts: 

(1) A physical inspection to assure that the sensor was installed properly 

(2) A performance test to establish and document the level of performance 
 2-6 

2.3.6.2 Performance Testing 

Performance testing should be conducted every 6 months or whenever a system or component 

is returned to service after modification, repair, maintenance, or an inoperable state. The 

performance test should include the use of the documented levels of performance from the 

original acceptance testing to verify that the system or component is still performing adequately. 

2.3.6.3 Operability Testing 

For systems or components in continuous operation, operability tests should be performed 

weekly to confirm that the sensors are operational and that alarms are communicated to the 

alarm station display system. These tests should be scheduled such that all sensors are tested 

at least once every 7 days. It is recommended that testing be performed on a portion of the 

total sensors over a distributed time period so that some sensors are tested during different 

times of the day within the 7-day timeframe. Subsequent testing should ensure that each 

sensor is tested during a different time of day than the previous test conducted. When 

conducting perimeter IDS operability testing in conjunction with perimeter assessment 

equipment testing, varying the time of day a sensor is tested enables the verification of 

assessment capabilities during the varied illumination conditions of daylight and at night. 
 3-1 

3. EXTERIOR DETECTION SENSORS 

3.1 Microwave Sensors

3.1.1 Principles of Operation and Performance 

Microwave sensors are motion detection devices that flood a specific area with an electronic 

field. A movement in the area disturbs the field and generates an alarm. Microwave sensors 

are typically used for detection in long, flat, narrow perimeter zones. (See Figure 1.) They are 

classified as an active, visible, volumetric, freestanding, and line-of-sight sensor. 

Figure 1: This photo depicts the application of microwave sensors within a perimeter intrusion detection and 

assessment system (PIDAS). Note that the drawn-in detection zone goes from the front microwave to 

another that is approximately 90+ meters (300+ feet) away. The middle microwave transmits to a unit behind 

the photographer. This configuration is referred to as a “basketweave” layout. 

Microwave sensors transmit microwave signals in the “X” band. These signals are generated by 

a diode operating within preset limits that do not affect humans or the operation of pacemakers. 

The effective detection zone width and height of a given microwave system will largely depend 

on the mounting height of the antennas when operating over the same type of surface at the 

same range. The mounting height is measured from the center of the antenna aperture to the 

ground. When properly aligned, the maximum detection height and width will occur at 

midrange. During installation in the field, antenna heights can be adjusted for maximum signal 

while monitoring the signal at the receiver. Most manufacturers indicate the linear operating 

range to be approximately 100–150 meters (328–492 feet) when detection of a stomachcrawling intruder is a requirement. Detection zone sizes are normally stated for midrange 

between the transmitter and receiver at the maximum antenna separation. 
 3-2 

3.1.2 Types of Microwave Sensors 

Microwave systems are found in two basic configurations: 

(1) bistatic, consisting of a transmitter and receiver antenna located at either end of a 

perimeter sector 

(2) monostatic, which uses a transceiver 

The bistatic microwave link consists of a transmitter at one end of a long, flat location and a 

receiver module at the other end. The transmitter emits a modulated, low-power signal in the 

microwave frequency band. The signal at the receiver antenna is combined in a vector 

summation of the direct line-of-sight signal and the reflected signals from the ground and nearby 

objects. The receiver monitors this signal for small changes that occur when objects move in 

the detection zone of the sensor. When the changes in the zone exceed an established 

threshold, an alarm is generated. 

Automatic gain control circuitry is used to allow the microwave sensor to compensate for very 

slow changes in signal because of environmental conditions. 

The size and shape of the detection zone are determined by the antennas, the transmitted 

frequency, and the distance between the antennas. The detection zone typically resembles an 

oblate spheroid, much wider and taller in the middle of the detection zone and narrowing on 

each end. (See Figure 2.) 

Figure 2: This diagram depicts the detection zone of a typical bistatic microwave. 

A monostatic microwave unit consists of a transmitter and receiver located in the same unit. 

(See Figure 3.) The two types of monostatic microwaves are amplitude modulated (AM) and 

frequency modulated (FM). AM monostatic microwave systems detect changes in the net 

vector summation of the received signal, similar to a bistatic system. FM monostatic systems 

operate on a pulsed Doppler principle and thus can determine range information. Some pulsed 

Doppler microwave sensors can be set up to only detect motion moving toward or away from 

the sensor in order to help minimize nuisance alarms. These are finding usage in some 

specialty applications, such as on ladders or stairs where the adversary has only limited 

approach options. 

In general, the useful range of a monostatic microwave is considerably less than that of a 

bistatic system. Monostatic microwave sensors are usually recommended only for application in 

areas inappropriate for a bistatic microwave. 

Figure 3: This diagram depicts the detection zone of a typical monostatic microwave. 
 3-3 

3.1.3 Sources of Nuisance Alarms 

While a microwave works fairly well in most weather conditions, some types of weather 

extremes may cause nuisance alarms, in particular, the first few seconds of a hard rain. 

Normally, after the rain has started, the sensor recognizes and adapts to the rain. Large 

puddles of standing water can cause nuisance alarms if wind creates ripples in its surface. 

Running water is also a major source of nuisance alarms if proper drainage is not designed into 

the sensor zone. 

Most flying debris, such as leaves, paper, cardboard, and tumbleweeds, will not cause an alarm 

because these objects are not reflective. However, if these same objects were wet or icy, they 

would likely cause the system to alarm. An aluminum can, because it is highly reflective, will 

also cause an alarm. 

While an animal as small as a mouse or a single bird will not normally be detected by a 

microwave, animals the size of a rabbit or a flock of birds likely will be detected. 

If the fabric of a chain-link fence moves, the reflection may cause an alarm, even though the 

fence is outside of the volume of detection. 

3.1.4 Characteristics and Applications 

The following list describes characteristics and applications of microwave sensors: 

 The microwave is a volumetric sensor and has a large detection pattern. 

 To a potential adversary, the detection pattern of the microwave is unknown. 

 Microwaves may be stacked to create a much taller detection pattern. 

 The microwave works well in most weather conditions. 

 The microwave is appropriate for long, narrow, flat zones. 

 The microwave will be able to detect within snow, as long as the antenna is not blocked. 

 Microwaves are typically vulnerable to crawlers immediately in front of both the 

transmitter and receiver. 

 Microwave sensors do not work well in extremely heavy fog or in a wet, heavy snow. 

 Microwaves will not perform well in a rainy climate when drainage is poor. 

 Microwaves perform less optimally in areas of heavy snow. 

 Microwave sensors do not lend themselves to use in areas where the terrain has large 

variations. 

 Site preparation for a microwave installation can be difficult because of the requirement 

for very flat terrain. 
 3-4 

 Microwaves will not work well in a zone between two fences that are not at least 6 

meters (20 feet) apart. 

 Vulnerabilities have been noticed when microwaves are operated near runways at 

airports. 

3.1.5 Installation Criteria 

Typically, a bistatic microwave perimeter detection system should be installed to operate 

effectively at a distance between antennas of not more than 120 meters (approximately 

328 feet). Successive microwave links and corners should overlap to eliminate dead spots 

(areas where the microwave beam cannot detect) below and immediately in front of transmitters 

and receivers. The required amount of overlap of successive links is contingent on the antenna 

pattern, alignment, and mounting height but may be up to 10 meters (approx. 32.8 feet) in 

length for some models. Overlap should be adequate to provide continuous detection of 

crawling intruders over the entire sector. (Refer to Figure 4 and Figure 5.) 

PIDAS exterior fence 

PIDAS exterior fence 

PIDAS interior fence 

PIDAS interior fence 

Basket Weave Overlap 

Parallel Overlap 

one sector

one sector

Figure 4: Examples of possible microwave sensor layouts. 
 3-5 

Figure 5: Example of a corner setup of microwave sensors that provides overlap to decrease the possibility 

of an adversary crawling beneath the beams. 

There should also be an area at each end of the sector where the crawler is detected by both 

microwave links to ensure continuous detection between adjacent sectors. 

Since the bistatic transmitter/receiver link is a line-of-sight system, variations in ground level 

(e.g., ditches and valleys) could allow some intruders to crawl under the beam; bumps or 

obstructions may create shadows in the beam that the adversary could crawl behind; and 

variable obstructions (e.g., snow drifts or accumulations) may interrupt the beam. To prevent 

passage under the microwave beam, variations in the ground should be leveled, ditches should 

be filled, and obstructions should be removed so that the area between the transmitter and 

receiver is clear of obstructions and free of rises or depressions. Overlaps should be adequate 

to allow the microwave beam to expand enough to detect an intruder attempting to jump over 

the microwave beam. 

In zone overlap areas, the equipment for the overlapped zones should usually both be 

transmitters, or both should be receivers to minimize the interference between the successive 

links. Different modulation frequencies are used for microwave links in adjacent sectors to 

prevent interference from other microwave transmitters. 

Because standing water can be a major source of nuisance alarms, proper drainage is required 

to prevent standing water and to prevent erosion that may provide the adversary with low spots 

where crawling is more difficult to detect. Gravel is often used for the perimeter surface to allow 

water to drain quickly and minimize erosion. Solid surfaces, such as asphalt or concrete, may 

prevent erosion problems but may actually cause a higher nuisance alarm rate during periods of 

heavy rain, because of the rain bouncing off of the surface. 

Each microwave unit should be mounted securely on rigid posts and aligned according to the 

manufacturer’s installation criteria. The mounting pole of the microwave for the adjacent sector 

should not provide an aid to the adversary attempting to jump over the microwave beam. (Refer 

to Figure 6.) Cutting down the mounting pole or using a spike or other attachment that does not 

allow the adversary a solid jumping platform may be required. 
 3-6 

Figure 6: This scene taken from a test of microwave sensors shows the possibility of an attacker using the 

microwave structure as an aid to jump over its own detection zone. Note: The microwave patterns shown in 

the photo were added for illustration purposes. 

Because of variances in the antenna patterns of different microwave systems, the height may 

need to be varied slightly to obtain coverage adequate to detect crawling intruders. Accordingly, 

the mounting mechanisms for a system should permit adjustment of antenna height and position 

to correct poor performance or alignment. 

Wiring should be protected with conduit, using flexible conduit near the sensor to allow 

alignment and adjustment of the antenna. 

The clear area (the space between the two PIDAS fences) should be sufficiently wide to 

preclude the generation of alarms by legitimate movements near the microwave link 

(e.g., personnel walking or vehicular traffic) and to preclude system degradation caused by 

reflections from any structure, such as the perimeter fence. The manufacturer should provide 

approximate dimensions of the microwave pattern. Since the beam is relatively wide, care 

should be taken to ensure that reflections from authorized activities do not create nuisance 

alarms. With the microwave link installed inside a perimeter barrier or between a double 

perimeter barrier, the transmitter and receiver should be positioned so the height of the zone of 

detection will detect anyone jumping or attempting to bridge over the microwave beam into the 

protected area from atop perimeter barriers such as fences or walls. Typically, the distance 

between a chain-link security fence with an overall height of 2.4 meters (8 feet) and the center 

of the microwave beam should be a minimum of 2.4 meters (8 feet). In addition, the microwave 

link should be positioned within the isolation zone to maximize the zone of detection and 

enhance assessment once detection is made. Neither a transmitter nor a receiver should be 

mounted on a fence. 
 3-7 

Stacking of microwave sensors is one means of increasing the detection zone height of the 

system to enhance its detection capabilities. The stacking technique places a microwave link 

close to the ground to provide better crawl detection and one or more links higher to improve 

detection of jumping or bridging. (Refer to Figure 7.) The stacked units may use different 

carrier frequencies, different antenna polarization, or multiplexing to prevent interference 

between the microwave links. 

Figure 7: An example of stacked microwave sensors. Note that the possibility of crawling beneath the 

microwave detection zone has been reduced significantly because of the microwave sensor that is installed 

close to the ground. 

3.1.6 Testing 

A regular program of testing of sensors is imperative for maintaining them in optimal operating 

order. Three types of testing need to be performed during the life of a sensor: acceptance 

testing, performance testing, and operability testing. 

3.1.6.1 Acceptance Testing 

When a microwave sensor is first installed, it should be tested in order to formally “accept” the 

sensor as part of the physical protection system. Acceptance testing consists of two parts: a 

physical inspection and a performance test, as follows: 

(1) A physical inspection to ensure that the microwave unit was installed properly consists 

of the following: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify sector intersection spacing. 

 Verify that signal and power wires are routed in the conduit. 

 Verify proper power levels (voltage and amperage). 

 Verify correct wire connections. 
 3-8 

(2) A performance test establishes and documents the level of performance. The following 

section describes the type of tests that are recommended for the microwave. 

3.1.6.2 Performance Testing 

Generally accepted performance criteria for a microwave detection system are that the system 

should be capable of detecting an intruder weighing a minimum of 35 kilograms (77 pounds) 

passing through the zone of detection between the transmitter and receiver, including the area 

in front of both the transmitter and receiver, whether the individual is walking, running, jumping, 

or crawling. Provisions should be made to ensure detection in spite of the dead spots in front of 

transmitters and receivers. 

3.1.6.2.1 Procedure 1: Crawl Tests

Conduct 30 crawl tests within the detection zone/sector to verify that the probability of crawl 

detection is at least 90 percent at a 95-percent confidence level. 

Each sector should be tested 30 times at points along the length of the microwave detection 

zone, though the overlap areas of two microwaves should be the primary focus. 

As it can be difficult to locate an adult of approximately 35 kilograms (77 pounds) and because 

crawling is viewed as the most favorable form of spoofing a microwave sensor, most sites use a 

30-centimeter (approx. 11.8 inches) diameter aluminum sphere to simulate crawl tests. (Refer 

to Figure 8.) The sphere diameter represents the cross-sectional area (at microwave 

frequencies) of an intruder lying parallel to the beam centerline. Pulling the sphere across the 

zone at slow speeds can determine if the microwave sensor is capable of detecting a small, 

stealthy individual. Because the radar cross-section of the sphere does not change with its 

orientation and the physical demands on the tester are much less than performing actual crawl 

tests, the sphere test can yield more repeatable results that eliminate variability because of the 

size and skill of actual crawling individuals. 

Figure 8: An aluminum sphere is commonly used for testing the potential success of a crawler against 

a microwave detection system. 
 3-9 

If the aluminum sphere is not detected until after it has been pulled across the centerline of the 

microwave detection zone, this often indicates an area of weak detection that may need to be 

addressed through additional adjustment of the sensor. A small individual can perform actual 

crawls in limited locations to supplement the sphere drag testing, perhaps testing in areas 

where the sphere was not detected until after it had crossed the beam centerline. 

The aluminum sphere should be mounted on a nonmetallic platform or base that does not raise 

the height of the sphere or increase the radar cross-section. The base is usually a sled but is 

sometimes wheeled, which helps prevent the sphere from becoming dented. As the sphere 

begins to get dented, the radar cross-section increases and it no longer accurately represents a 

small individual. The cord used to pull the sphere across the zone should be nonmetallic so as 

not to affect the beam. Nylon sash cord can be used effectively. The cord should be long 

enough to allow the testers to be completely out of the microwave detection area. (Refer to 

Figure 9.) 

Figure 9: Testing microwave sensors with an aluminum sphere. 

3.1.6.2.2 Procedure 2: Other Tests

Another method of performance testing incorporates the use of a combination of the common 

defeat methodologies (walking, running, jumping, climbing, crawling and bridging) within each 

detection zone to verify a system’s detection capability. Each sector should be tested 30 times 

at points along the length of the detection zone. Walk tests may be useful for mapping out a 

sensor’s detection pattern for the purpose of identifying antenna misalignments, but the 

detection of a walker is not normally considered “challenging” for a microwave detection system. 

Jumping, climbing and bridging tests should be performed to verify that the height and overlap 

of the beam is adequate. Jumps, assisted, unassisted and using nearby objects as a jumping 

platform should be performed to verify that detection is adequate. Run tests are suggested 

because some microwave sensors have a high-speed cutoff in order to eliminate some types of 
 3-10 

nuisance alarm sources. When using various defeat methodologies for performance testing, 

each defeat methodology should be used in the different areas of the zone being tested. 

3.1.6.3 Operability Testing 

The operability test may be conducted by walking into the expected detection zone of the 

microwave. 

If no alarm is received, a maintenance request should be immediately generated and 

implementation of compensatory measures should be considered based on site-specific 

requirements. 

3.1.7 Maintenance 

Recommended maintenance procedures include the following: 

 Vegetation or erosion in the areas of the microwave detection pattern should be 

checked. 

 If the sensor has not been experiencing any recent problems (i.e., failure to alarm during 

a walk test) and if the most recent performance test was successful, there is then no 

reason to work on the alignment or sensitivity setting of the unit. 

 At least one manufacturer recommends waxing the antenna covers periodically. 

 Looking for any evidence of damage to the sensor or tampering with the device. 

3.2 Electric Field Sensors

3.2.1 Principles of Operation 

Electric field sensors (often referred to as e-field sensors) consist of posts or other supports with 

wires strung between them. (Refer to Figure 10.) In the sensor’s most basic form, there is one 

field wire and one sense wire. An oscillating electrical signal is applied to the field wire, which 

establishes an electromagnetic field around the field wire. A sense wire is located close to and 

parallel to the field wire. Some of the field energy is coupled to the sense wire. A processor 

analyzes the received energy and monitors changes to the energy level. Most of the signal 

coupling results from capacitive coupling. The energy level coupled to the sense wire is 

dependent on the electrical ground (also referred to as earth ground), the spacing of the wires, 

the length of the wires, and the dielectric of the medium (air) between the wires. A human body 

is mostly water and the dielectric of water is about 100 times greater than that of air. As an 

intruder approaches the wires, the signal coupled to the sense wire is disturbed because of the 

higher dielectric of the intruder’s body and because the intruder is partially in contact with an 

electrical ground provided by the earth. Figure 11 shows a typical electric field sensor’s zone of 

detection. 
 3-11 

Figure 10: Example of an electric field sensor installed in a test environment. 

Field 

wires 

Sense 

wires 

Zone of Detection 

Figure 11: A cross-section of an electric field sensor’s zone of detection. 

Older electric field sensor processors were simply based on detecting a sufficient change in 

amplitude (threshold) of the analog signal that did not occur too fast or too slowly (bandpass 

filtering) to be considered an intruder. Unfortunately, many environmental sources could cause 

disturbances that would meet these simple conditions for an alarm. Newer models employ 
 3-12 

digital processing and sophisticated pattern recognition software to generate an alarm. This 

change has resulted in a significant reduction in nuisance alarms for new electric field sensors 

while maintaining good levels of detection. 

Electric field sensors are volume detectors. They can usually follow the terrain where they are 

installed. While their characteristic wires give them the appearance of a line-type sensor, the 

electric field generated by these wires makes the zone of detection extend well beyond the 

wires. Electric field sensors can have a very wide detection volume (up to 2 meters or 6.5 feet 

wide) as well as a very tall detection volume (4.9 meters or 16 feet or more), based on the 

installation configuration. To achieve these heights, combinations of multiple field and sense 

wires can be incorporated within a single electric field system. 

3.2.2 Types of Electric Field Sensor Applications 

Electric field sensors can be installed in a freestanding configuration on their own posts. They 

can also be installed on chain-link fences, on the top of building roofs, on the side of building 

walls, and on the top of concrete walls if special supports are incorporated. (Refer to Figure 12.) 

Various wire configurations can be used to accommodate these mounting situations to yield the 

desired detection height and volume. Because of their adaptability to various vertical and 

horizontal surfaces, e-field sensors may be applicable to areas that are not compatible with the 

use of other sensors. 

Figure 12: Various configurations for electric field sensors. 

3.2.3 Sources of Nuisance Alarms 

Proper installation of electric field sensors is critical to minimizing nuisance alarms. Any 

ungrounded metal object in the vicinity of an electric field sensor that can change potential can 

cause a nuisance alarm. For example, a chain-link gate may have grease in the hinges that 
 3-13 

partially insulates it from the rest of the fence, but small wind-induced motion may occasionally 

result in contact between the gate and the metal of the hinge, which has the potential to cause a 

nuisance alarm. Attaching the sensor ground and all metal within the vicinity to a common 

electrical ground (earth ground) can reduce nuisance alarms. 

Weather-related sources of nuisance alarms include rain, as well as wet or melting snow. 

During the start of a heavy rain, a few nuisance alarms should be expected. However, the 

newer electric field processors can quickly recognize the pattern of rain and, after recognition, 

will ignore it while still maintaining detection levels. During snowstorms, even with the bottom 

wire covered with snow, the sensor should still detect in an acceptable manner. During very 

heavy, wet snow, or when the snow is melting and possibly creating conduction paths to 

ground, there is a potential for nuisance alarms. 

Small animals that touch the wires and larger animals that approach the wires may cause 

alarms. The use of nuisance control fences can significantly reduce these alarms. A single bird 

landing on a wire generally will not cause an alarm, but a flock of birds may. The wires of an 

electric field sensor are small enough that larger birds generally do not land on the wires. 

Wet plants or wet weeds that touch the wires can also cause alarms. The use of nuisance 

control fences (to reduce blowing debris) and maintaining a sterile area (to prevent plant growth) 

near the wires can significantly reduce these nuisance alarms. Figure 13 shows an example of 

nuisance alarm sources. 

Figure 13: Sources of nuisance alarms for electric field sensors include flocks of birds; wet, heavy snow; 

vegetation; and animals that may touch the wires. 
 3-14 

3.2.4 Characteristics and Applications 

The following list describes the characteristics and applications of e-field sensors: 

 E-field sensors operate well in most environments. 

 Configurations can be tuned to have a very large and relatively even detection volume, 

which can make an e-field sensor very difficult to defeat or circumvent. 

 A variety of mounting configurations can be used (i.e., the sensor can be fence mounted 

on an existing chain-link fence (with some reduction in detection volume), or it can be 

mounted on its own posts in a freestanding configuration (preferably between two 

fences). 

 E-field sensors can be installed on walls and roofs, which makes it easier to maintain a 

continuous line of detection if there is a building within the perimeter. 

 E-field sensors can follow uneven terrain with posts spaced approximately every 6 

meters (20 feet); the wires can be routed up and over gentle hills and valleys. 

 The installation of e-field sensors usually requires a factory-trained installer or 

experienced alarm technician to perform installation. 

 As the horizontal parallel wires of an e-field sensor naturally form a type of fence, this 

presents an operational barrier to the entry of authorized vehicles or personnel. Where 

personnel or vehicle access through the perimeter of a protected area is required, a 

different sensor (other than the e-field sensor) must be incorporated to allow for 

continuous and even detection through the entry area. 

 Because this sensor is a volumetric sensor, large moving metal objects near the sensor 

can cause nuisance alarms. If the e-field sensor application includes an area where the 

frequency of vehicles passing close to the sensor could cause numerous alarms, a 

different sensor type should be considered. 

 A potential defeat method for an e-field sensor is an intruder slowly attempting to crawl 

under the bottom wire. The bottom wire height should be evenly parallel to the ground 

and low enough to detect all crawlers. There should be no areas, such as a ditch 

caused by erosion or other low depression, where the wire height may create an area of 

vulnerability. 

3.2.5 Installation Criteria 

Many components are required for an e-field sensor installation. Figure 14 shows some of 

these parts, which include the sense wire, various insulators, posts, and support hardware. 

Proper system installation is vital for proper performance; therefore, installers should be factory 

trained or experienced technicians and should follow manufacturer installation instructions. 
 3-15 

Figure 14: Main components of an electric field sensor installation. 

The single most important detail in the installation process is that every piece of equipment or 

hardware must be connected to a common ground. This includes any electrically conductive 

structures or objects that are in the vicinity of the sensor system. The manufacturers of electric 

field sensors provide installation instructions, which specify grounding procedures that include 

the installation of a common ground wire and copper-clad steel rods that are driven into the 

ground. 

Installed configurations may be freestanding (where the wires are mounted on their own 

dedicated poles) or may be attached to an existing sturdy fence. A freestanding installation is 

usually considered preferable; installation on a chain-link fence will effectively cut out half of the 

detection volume—that half on the side of the fencing that does not contain the electric field 

sense wires. 

An electric field sensor system may also be mounted or attached directly to the wall or roof of a 

building. If the wall or building is not constructed of a material that can provide an adequate 

electrical ground (earth ground), a grounded metal screen can be installed under the sensor that 

will provide the needed ground reference. 

A cleared area must be created where the sensor system will reside. Ideally, this should be an 

area where access is not possible by passing pedestrians or animals. Weeds near an electric 

field sense wire must be eliminated or kept well trimmed. 
 3-16 

3.2.6 Testing 

Three types of testing need to be performed during the life of a sensor: acceptance testing, 

performance testing, and operability testing. 

3.2.6.1 Acceptance Testing 

When a sensor is first installed, it should be tested before the formal “acceptance” of the sensor 

as part of the physical protection system. Acceptance testing consists of two parts: 

(1) A physical inspection to ensure that the sensor was installed properly, as follows: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify sector intersection spacing. 

 Verify that signal and power wires are routed in conduit. 

 Verify proper power levels, both voltage and amperage. 

 Verify correct wire connections. 

(2) A performance test to establish and document the level of performance (see next 

section). 

3.2.6.2 Performance Testing 

System or component modifications such as processor replacement or adjustment, wire 

spacing, or height adjustments, or any change to the sensor (or in the vicinity of the sensor) that 

might affect the detection capability would require performance testing to verify system 

performance. 

The performance test should include a visual inspection of the sensor and of the general area 

where the sensor is installed. The test should record all relevant processor readings and 

compare these to the last recorded readings. It should measure the lower wire height at all the 

posts and midway between the posts and then compare these values to previous values 

documented when the sensor system was judged to have been performing optimally. 

Because an electric field sensor is a volume detector, it will detect the approach of an intruder at 

some distance from the sense wires and an intruder penetrating the wire array. Though these 

systems or sectors of these systems may provide detection of an approach at some distance, in 

some cases the zone of detection may be such that detection occurs upon penetration of the 

zone between or in close proximity to the senor wires. The performance test must confirm that 

penetrations or attempted penetrations of the wire array that forms the electric field sensor 

system are detected at the required level. To ensure the overall effectiveness of an electric field 

system, performance testing should incorporate the use of a combination of common defeat 

methodologies (crawling, walking, jumping, climbing, and bridging) applicable to an electric field 

system within each detection zone. Each sector should be tested 30 times at points along the 

length of the electric field detection zone. 

When using various defeat methodologies for performance testing, each defeat methodology 

should be used in the different areas of the zone being tested. If each of the 30 tests result in a 

detection, the electric field sensor sector has been confirmed to have at least a 90-percent 
 3-17 

probability of detection at a 95-percent confidence level. Particular attention should be given to 

any low depressions and to the areas where sectors overlap (one of the sectors must alarm in 

this area). 

As an electric field sensor is most susceptible to defeat by crawling, during performance testing 

the 30 test attempts may include more crawl tests than the other defeat methodologies. For 

crawl tests the tester should lie down flat on the ground with his or her head toward the wires 

but starting outside the detection volume of the sensor. The tester should weigh 35 kilograms 

(77 pounds) or more. The tester should crawl slowly (approx. 2 to 6 inches per second or in 

accordance with manufacturers specifications) under the sense wires, keeping the motions as 

smooth as possible and stopping when a detection occurs (See Figure 15.). The crawler must 

fully penetrate the wire array (to a point beyond the detection volume on the opposite side of the 

sensor) to declare a nondetection. 

Figure 15: An example of the crawl-test procedure. 

For fence-mounted sensors, it is not possible to exit the detection volume because of the 

physical barrier of the fence. In this case, the sensor is not considered defeated simply by the 

tester’s head or arm penetrating the plane of the wire array without a detection. The tester 

should continue to move their body through the wire array attempting complete penetration. 

Also, because an intruder must take some action to also penetrate the fence, such as cutting a 

hole in the fence or standing up to climb the fence, the intrusion test should include a 

reasonable simulation of the motion and tools required to simulate an intruder climbing over the 

fence, cutting through the fence, or going under the fence.

3.2.6.3 Operability Testing 

Operability tests should be conducted by walking to the immediate vicinity of the electric field 

sensor wires and attempting to penetrate the zone of detection until an alarm is communicated 

and received in the alarm station. 

During operability tests, the area in which the system or components are being tested should be 

surveyed for evidence of damage to equipment or possible tampering that may have occurred. 

3.2.7 Maintenance 

The routine maintenance required is mainly associated with inspecting the components and 

inspecting the near vicinity for ungrounded metal objects, plant growth, and/or debris. The 

sense wires of an electric field sensor are tensioned so that they vibrate at a frequency that is 

outside the signal frequency of interest. Verifying the tension of the sense wires and the 
 3-18 

inspection of system components should be part of the regular maintenance and may be 

combined with the scheduled testing of the sensor. An increase in nuisance alarms indicates 

the need for physical inspections. 

Routine maintenance inspections should do the following: 

 Inspect for weed growth, sterilize the soil or remove any growth near the sense wires. 

 Inspect for and remove any debris that could cause nuisance alarms. 

 Inspect the wire for proper tension and for any poor and/or broken connections. 

 Inspect and clean dirt or debris (e.g. insects, spider webs, etc.) from insulators as 

needed. 

 Inspect all mechanical parts for damage. 

 Inspect all sensor electrical ground (earth ground) connections. 

 Inspect nearby metallic objects for good ground connections. 

 Confirm wire heights by looking for eroded or low areas where the wire height may be 

too high. Document the maximum bottom wire height determined to be acceptable to 

provide adequate detection.

3.3 Ported Coaxial Cable Systems

3.3.1 Principles of Operation 

A ported coaxial cable system (commonly referred to as “ported coax”) is a terrain-following, 

volumetric, covert intrusion detection system (IDS) that consists of two buried, ported coaxial 

cables and a processing unit. (Refer to Figure 16.) The processor contains a transmitter, a 

receiver, various amplifier and filter circuits, and a microprocessor with associated hardware 

and software. This system is an active electromagnetic sensor using two identical “leaky” 

coaxial cables (the shielding of the cable has holes or “ports” in it) buried parallel in the ground. 

The transmitter portion of the processor is connected to one cable, and the receiver is 

connected to the other. 

Because the outer conductor of the cables is ported (i.e., it contains closely spaced small holes 

or gaps in the shield that allow radiofrequency (RF) energy to radiate), any electromagnetic 

energy injected into the transmitter cable is radiated into the surrounding medium, and some of 

this energy is coupled into the receiver cable through its ported shield. Thus, a static field of 

coupling is established between the cable pair. When an intruder enters the established field, 

the coupling is perturbed, and the change in received signal is digitally processed. Changes in 

this electromagnetic field that exceed threshold levels cause an alarm. 
 3-19 

Figure 16: An illustration of the covert zone of detection for a ported coax sensor. 

Ported coax sensors are sensitive to changes of dielectric or conductivity within the detection 

zone and are insensitive to seismic noise. The cross-section of the detection zone is somewhat 

elliptical and can be up to 1 meter (3 feet) high and 3 to 4 meters (9 to 12 feet) wide. Detection 

is achieved both above and, to some extent, below the ground. (Refer to Figure 17.) Tests 

have shown that both the detection zone size and detection sensitivity vary along the sensor 

cables. Such variance may result from several causes, such as phase cancellations, buried 

metallic objects, variation in cable separation or burial depth, and variable soil composition; 

therefore, it is important to identify the low-sensitivity areas and to adjust the sensitivity or the 

installation to achieve an adequate detection volume. 

Figure 17: A typical installation and detection envelope (green oval) for a ported coax sensor.

0.9 – 2 m

(3 ft – 6 ft, 7 in.)

.7 m

(2 ft, 3 in.)

.23 m

(9 in.)

2 – 3 m

(6 ft, 7 in – 9 ft, 10 in.)

Transmit

cable Receive

cable

Average 1 m

(3 ft, 3 in.)
 3-20 

Soil characteristics affect the signal strength of the ported coax receiver signal. However, even 

at sites where soil attenuation is relatively large, operational ported coax systems have been 

implemented. Variations in soil moisture are reflected in changes in ported coax signal 

attenuation. Wet soil is more conductive than dry or frozen soil; therefore, seasonal changes 

may be accompanied by changes in ported coax detection sensitivity. Recalibration is often 

required to account for seasonal changes. 

3.3.2 Types of Ported Coaxial Cables Available 

Either pulsed or continuous wave RF energy can be used in a ported coax sensor. 

The pulsed system operates in principle as a guided radar, and therefore, both detection and 

location of the intruder (i.e., location along the cable length) are determined. Because of the 

ranging capabilities of this type of system, detection zones can be set in the software, enabling 

the configuration of more than the traditional two sectors per processor. This is possible 

because of the sensor’s capability to divide each sensor cable into small subcells, usually 

1 or 2 meters (3.28 or 6.56 feet) in length. Each of these subcells can be independently 

adapted to the site conditions and analyzed. This capability enables the alarm threshold to be 

varied in each of these subcells, providing uniform detection along the entire length of the cable. 

Continuous wave ported coax sensors perform no range processing; therefore, they transmit 

continuously or during specified times. The frequency of operation is approximately 

40 to 60 megahertz. There is only one alarm threshold per set of sensor cables, and the cables 

are the length of the sector. The continuous wave system detects the intruder but does not 

localize the presence along the cable length. Each processor can monitor one or two channels 

(or sectors) and provides an alarm indication if an intrusion occurs anywhere in the zone of 

detection. 

Figure 18 shows examples of different ported coax cables. 

Figure 18: Examples of ported coax cables. 
 3-21 

3.3.3 Sources of Nuisance Alarms 

The nuisance alarm rate for ported coax sensors is relatively low in a well-designed and 

carefully installed system, but several environmental and installation factors can affect the rate. 

(See Figure 19.) The major source of nuisance alarms is surface water from rain or melting 

snow, which makes proper drainage essential. Both flowing water and standing water that 

produces ripples when the wind blows will contribute to movement that is targeted by the 

sensor. 

Movement of metallic objects (e.g., automobiles and fences) or dielectric objects (e.g., animals, 

people, and plants) in the vicinity of the sensor cables can result in alarms. Small animals 

weighing less than 4 kilograms (9 pounds) generally do not cause alarms, unless they cross the 

sensor cables in groups. The magnitude of the nuisance alarm rate also depends on the type of 

sensor, the installation method, maintenance practices, and the sensitivity setting. 

Figure 19: Sources of nuisance alarms for ported coaxial cable detection systems include nearby moving 

vehicles, larger animals, large and wet plants moving in the wind, and moving water, as well as the ripples 

caused by wind blowing across standing water. 

3.3.4 Characteristics and Applications 

The following list describes the characteristics and applications of ported coax sensors: 

 They have volumetric, covert detection capabilities. The intruder must guess where the 

detection envelope is in order to defeat the sensor by bypassing it. 

 They are often used where esthetic considerations dictate a sensor technology that is 

unseen by the general passerby. 
 3-22 

 They are very effective in detecting the crawling intruder and therefore are often used as 

a complementary sensor to other sensor technologies, such as microwave, e-field, or 

active infrared technologies, that may have a weakness to this method of attack. 

 The pulsed ranging systems provide the added benefit of allowing the use of a lower 

number of processors to monitor multiple perimeter sectors. 

 Even though the detection envelope of the ported coax sensor can be relatively wide in 

volume (depending on cable spacing), it is limited in height, and any method allowing an 

intruder to bridge over it could result in a successful defeat of the system. If not 

protected, nearby fences and utility poles can be used for this purpose. For this reason, 

it is not generally recommended to install this sensor as a stand-alone system around a 

perimeter for high-security applications. 

 The installation of this system requires extensive trenching. In addition, once the system 

is installed, any needed maintenance of the cables or decouplers buried in the ground 

could require significant effort to locate and repair these components. 

 Even though the system is terrain-following and does not require a straight line of sight, 

site preparation is very important to ensure the provision of proper drainage to reduce 

nuisance alarms caused by runoff. 

 Depending on location, installing a good fence system to isolate the cables from animals 

is also important to reduce the nuisance alarm rate to an acceptable level. 

3.3.5 Installation Criteria 

Ported coaxial cable systems should be installed according to the manufacturer’s specifications. 

Generally, this type of system can operate in longer segments than other detection systems. 

However, it is recommended that detection zones be restricted to segments of 100 meters 

(328 feet) or less to facilitate assessment. The system is terrain-following and can be curved 

around corners as long as the minimum radius specifications are observed. The maximum and 

minimum separation of the transmitter and receiver cables can vary from approximately 

2 meters (6.6 feet) to being co-located in a single trench. The separation is dictated by the clear 

zone available and proximity to objects that may interfere with the sensor’s detection envelope. 

The lines are generally buried at a depth of .23 meters (9 inches). (See Figure 20.) 

The installation of ported coaxial cable perpendicular to buried metal conduit for electrical 

cables or metal pipes used for water or storm drains may degrade detection capabilities or 

cause nuisance alarms. Separation distances dictated by the manufacturer should be strictly 

observed. Soil conductivity should be considered when installing this type of sensor as it may 

reduce the detection volume. Soil found to have relatively high conductivity may cause the 

detection field to be reduced. Highly conductive soil contains concentrations of iron or salt. 

Moving objects in the zone of detection such as foliage, flowing or standing water, and grasses 

may create nuisance alarms. Rodents can chew through ported coaxial cable. 
 3-23 

Figure 20: Typical ported coax cable system installation. 

Sensor locations should be carefully selected to prevent nuisance alarms from such sources as 

personnel and vehicular traffic. Similarly, the cleared area above the sensor should be 

controlled to prevent the placement of objects within the area, even temporarily, which would 

degrade the detection zone. The ported coax cables should be installed on well-drained terrain 

cleared of trees, tall grass, and bushes. Freezing or thawing of the ground may affect system 

sensitivity. Neither the transmitter nor the receiver lines should be mounted above ground. 

The system should be installed, relative to perimeter fencing, so that the transmitter and 

receiver lines are positioned to prevent someone from avoiding detection by jumping over the 

electromagnetic field. Typically, the distance between chain-link security fencing with an overall 

height of 2.4 meters (8 feet) and the center of the detection zone should be a minimum of 

2.4 meters (8 feet). 

Fixed metal objects and standing water distort the radiated field, possibly to the extent of 

creating insensitive areas with no, or very low, detection. Nearby metal objects and utilities 

should be located outside the detection volume. This includes aboveground fences and poles, 

as well as underground water and sewer lines and electrical cables installed close to the 

surface. (Refer to Figure 21.) 

Manufacturer’s instructions should be followed when installing cable across concrete or asphalt 

areas. Particular attention should be paid to the binding agent and the application of epoxy over 

the cable groove after the cable is installed in the concrete or asphalt. 
 3-24 

Figure 21: Metal objects or utilities located within the detection volume of a ported coax system may create 

areas of poor detection. 

Criteria for ported coaxial cable system installation include the following: 

 Ensure that the ground in which a ported coaxial cable system is buried is firm and is not 

subject to movement. 

 Ensure that drainage is adequate because surface water (standing or flowing) can cause 

ported coaxial cable systems to generate false alarms. 

 Rodents can chew through ported coaxial cable—be aware of their burrows. 

 Avoid intersecting irrigation pipes and power lines with the coaxial cable, or ensure that 

separation distances specified by the manufacturer are observed. 

 Note that the detection zone may be elongated at curves. 

 In rare cases of extreme soil conditions (either very sandy or highly conductive), soil 

conductivity tests may be warranted to ensure that performance of the system is not 

compromised. 

3.3.6 Testing 

A regular program of testing sensors is imperative for maintaining them in optimal operating 

order. Three types of testing need to be performed during the life of a sensor: acceptance 

testing, performance testing, and operability testing. 

3.3.6.1 Acceptance Testing 

When a ported coaxial sensor is first installed, it should be tested in order to formally “accept” 

the sensor as part of the physical protection system. Acceptance testing consists of two parts: 
 3-25 

(1) A physical inspection to ensure that the sensor was installed properly consists of the 

following: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify sector intersection spacing. 

 Verify that signal and power wires are routed in the conduit. 

 Verify proper power levels (voltage and amperage). 

 Verify correct wire connections. 

(2) A performance test should establish and document the level of performance. Refer to 

the performance testing procedure (below) for a description of the recommended tests. 

3.3.6.2 Performance Testing 

A ported coaxial cable perimeter detection system should be capable of detecting an individual 

passing over the transmitter and receiver wires, whether the individual is walking, running, 

jumping, crawling, or rolling. 

The probability of detection is affected by the installation configuration of the cables, the system 

processor settings, soil conductivity, intruder orientation and speed, and the proximity of metallic 

objects. 

Testing should ensure that the device is capable of detecting the defined target with a 

site-specific probability of detection of 90 percent and a confidence level of 95 percent. The 

system should detect a person crawling, running, or jumping through any area of the detection 

volume. As such, performance testing should include these defeat methodologies. Testing has 

shown that a person using a “duck walk” profile (walking in a crouched position) to pass through 

the detection volume produces the smallest disturbance to the system. (Refer to Figure 22.) 

Sensor parameters should be set to detect this type of intrusion. 

Figure 22: The “duck walk” seems to produce the smallest disturbance in a ported coaxial system and 

is therefore ideal to use to test the system. 
 3-26 

3.3.6.3 Operability Testing 

Operability tests should consist of simple walk tests. The testing individual walks through the 

expected detection zone of a sensor and confirms that the alarm has been received at the alarm 

station. Operability tests should include a search for any evidence of damage to the sensor or 

tampering with the device. 

3.3.7 Maintenance Requirements 

Because the ported coaxial cables are buried and largely inaccessible after installation, 

maintenance to the system is minimal and involves the processor and the environment where 

the system is installed. Periodic checks should be conducted at least every 6 months and 

include the following: 

 If applicable, check terminations and/or decouplers between sectors of sensor cable that 

are located above ground for signs of wear or leakage. 

 Inspect the processor enclosure for any physical damage, water damage, corrosion, and 

ingress of insects. 

 Inspect the cable connections (coax, signal, or power) to ensure that they are tight. 

 Check the processor electrical ground (earth ground) connection for continuity and 

corrosion. 

 Check the input power for proper voltage. Check the battery status (if applicable). 

 Inspect the areas above the sensor cable for vegetation, debris, water accumulation, 

erosion, and settling of trenches. Correct as necessary. 

 Verify processor parameter settings to ensure that no undocumented changes have 

been made. 

3.4 Active Infrared Sensors

3.4.1 Principles of Operation 

Active infrared sensors are infrared beam-break sensors that detect the loss or significant 

reduction of infrared light transmitted to a receiver. Infrared light is invisible to the naked eye 

(though some digital or video cameras can detect it.) In its simplest form, an active infrared 

sensor consists of a single infrared transmitter that illuminates a single infrared receiver. In 

most security applications, an active infrared sensor will be composed of two columns of 

multiple infrared transmitters and multiple infrared receivers. This arrangement can provide a 

detection volume of significant height. The actual volume of detection is defined by all the 

beams (cylinders of infrared light) between the transmitters and the receivers and has the 

diameter of the receiver and transmitter’s optical lens. In a multibeam active infrared sensor, 

the actual volume of detection is composed of the numerous infrared beams that shine between 

the two columns. (See Figure 23.) The columns can be separated by up to 152 meters 

(500 feet) or more for some available types. The lowest beam is generally located within 
 3-27 

6 inches of the ground to detect crawlers; the spacing of the upper beams can generally be 

further apart. 

Figure 23: Multibeam active infrared sensor columns. (Red lines represent beams of infrared light.) 

Detection is based on blocking one or more of the beams for a specific period of time. Shorter 

measured beam interruption times are discounted to reduce nuisance alarms from small birds or 

blowing debris. Some models allow for user adjustment of this beam interruption time while 

others automatically vary the time depending on the number of beams interrupted. 

The infrared light is generally modulated and sequenced to reduce sensitivity to other light 

sources, which allows the sensor to operate in daylight as well as night. The sequencing for 

some models allows the use of multiple sensor sets without mutual interference, in case they 

happen to be within the field of view of an adjacent sensor set. 

3.4.2 Types of Active Infrared Sensors 

Active infrared sensors vary in size, beam configuration, range of operation, and operational 

features. They typically operate in ranges that allow them to be compatible with the sector 

lengths used in exterior perimeter applications. A single-beam unit will have limited application 

because of the small, single-beam detection volume. Many manufacturers provide sensors that 

can be combined to provide whatever detection height is required for an application. 

Some models can communicate to a remote laptop or other computer, a capability that allows 

them to be remotely configured or adjusted. Some models also have the capability for the user 

to turn off the lowest beam (for example, if the ground is covered by snow) to allow the 

remainder of the beams to operate normally. Most models have sealed beam assemblies or 

heaters that keep frost and condensation from forming on the optical covers and lenses. Some 

units can be sequenced so they will operate if their transmitters are in the field of view of an 

adjacent sector’s receivers. These and other features of the different models available should 

be considered, depending on the specific application and operational environment. 
 3-28 

Figure 24 below provides examples of the available designs of active infrared systems with 

varying transmitter, receiver and beam configurations. 

Figure 24: Active Infrared sensors vary in beam configuration. (T = Transmitter, R = Receiver) 

3.4.3 Sources of Nuisance Alarms 

Nuisance alarms can be caused by anything that can block or significantly obscure the infrared 

beam. Nuisance alarms from animals large enough to block the bottom beam can be minimized 

by installing the sensor between two fences. A single bird flying through an infrared beam will 

generally not cause an alarm, but a flock of birds may cause sufficient beam blockage to cause 

nuisance alarms. 

T 

T 

T 

T 

T 

T 

T 

R

R

R

R

R

R

R

12′′

7′′

12′′

12′′

12′′

12′′

12′′

T 

R 

R 

R 

R 

R 

R 

R

R

R

R

R

R

T

12′′

7′′

12′′

12′′

12′′

12′′

12′′
 3-29 

Blowing debris that blocks the bottom beam can cause alarms. Snow accumulation to a depth 

that covers the lower beam will cause a constant alarm that must be cleared by removing the 

snow or disabling the lower beam (on sensors with that capability). A disabled lower beam 

could allow an intruder to crawl under the sensor undetected; once the snow has been 

removed, the sensor should be restored to full operation. 

Heavy snow or fog thick enough to obscure visibility from transmitter to receiver may cause 

nuisance alarms. Bright lights (such as dawn or dusk sunlight during certain times of the year) 

that shine directly into the receiver can cause a nuisance alarm or a failure alarm. Some 

models have modules that contain both a transmitter and a receiver. In these models, the beam 

actually consists of two beams, one going in either direction. Both beams must be blocked or 

interfered with to cause an alarm. 

3.4.4 Characteristics and Applications 

The characteristics of an active infrared sensor include the following: 

 Line-of-sight operation 

 Volumetric detection that resembles line detection 

 Beam-break sensors (not field disturbance sensors) 

 Impervious to motion around it 

These characteristics make active infrared sensors especially useful in confined areas or in 

areas where there is much activity nearby. Thus, active infrared sensors are successfully used 

in entry control portals to substitute for a sensor that would block traffic flow or would have a 

high nuisance alarm rate because of activity in the area. They can operate over any surface 

and can “see” through chain-link fences, provided that a fence post or pole does not block any 

beams. 

Active infrared sensors are successfully used in perimeter applications. Because of their 

uniformity and detection height, active infrared sensors make a good complementary sensor to 

other types of sensors that have good crawl detection but lack the significant detection height 

that can be achieved with an active infrared sensor. 

Most models can operate well in a typical PIDAS sector length of 100 meters (328 feet); 

however, if local weather conditions have the potential to produce periods of reduced visibility, 

the installed operating distance should be reduced to 80 meters (approx. 264.2 feet) or less. 

(This is a good design practice for the alarm assessment (video) system as well, because video 

is also impacted by poor visibility.) Those models with a shorter operation range can employ 

multiple sets of active infrared sensors combined to accommodate the required sector length. 

Some active infrared sensors can be applied to special applications. They can be adapted to 

provide detection across doorways or windows, or across critical access doors. They can be 

installed across pedestrian and vehicle access openings in a PIDAS. Because of their modular 

nature and narrow detection width, active infrared sensors can be adapted to many areas that 

would be difficult or impossible for other types of sensors to monitor well. 
 3-30 

Because the detection characteristic of the active infrared sensor is a beam-break rather than a 

field-disturbance sensor, its detection volume can be more readily identified by a potential 

adversary. It can be closely approached without concern of detection as long as the beams are 

avoided. This means that if the detection height is configured to be 1.8 meters (6 feet) or less, 

an intruder aided by a step ladder could easily defeat the sensor by climbing the ladder and 

jumping over the top beam. Luckily, active infrared sensors can be configured to be 3.7 meters 

(12 feet) or more high. Jumping from this height becomes much more difficult; therefore, if an 

active infrared sensor is fairly short in height, it should be combined with a field disturbance 

sensor that can prevent a close undetected approach by an intruder, as well as detect attempts 

to crawl under the active infrared’s lowest beam. The height of the zone of detection of an 

active infrared system should account for the design and configuration of physical barriers within 

the vicinity of the zone of detection to ensure that the system provides protection from bridging. 

Because active infrared sensors are line-of-sight sensors, the ground between the transmitter 

and receiver columns must be relatively flat and planar (lying in a single geometric plane). Any 

low areas can be used to crawl undetected under the bottom beam. Even if the ground is flat 

and level, if a trench can be dug without detection, it may be possible for an intruder to quickly 

create a path onto the site under the bottom beam. It is recommended that if an active infrared 

sensor is used alone, a hard surface, such as a concrete sill or sidewalk, should be installed 

under the beams to prevent trenching, thus minimizing the potential for the system to be 

circumvented. 

Use of an active infrared sensor in locations that experience frequent deep snow, drifting snow, 

or dense fog must be carefully considered. During times that the lower beam is covered and 

disabled, crawl defeat is possible unless the active infrared sensor is used in combination with 

another sensor that can detect through the snow. In addition, during periods of dense fog, the 

sensor may go into constant alarm. During these periods, a complementary sensor that is not 

normally affected by fog would be very important in the detection of intruders. 

3.4.5 Installation Criteria 

A cleared area must be created around the sensor system location. Ideally, this area should be 

protected from passing pedestrians or animals. Isolating the detection equipment between 

fences provides this protection, as well as other security benefits. It is critical that weeds be 

eliminated in this area to avoid attracting animals and to prevent tall plant growth from blocking 

the infrared beams. 

The active infrared sensor should be mounted on a sturdy foundation that will not heave as the 

ground freezes or move in the wind. Most models have a field of view that will tolerate very 

small motion, but movement significant enough to misalign the beams will increase the sensor’s 

susceptibility to nuisance alarms. 

All alarm, communication, and power wiring to the sensor should be in buried conduit to reduce 

the risk of accidental damage or malevolent tampering. 

Active infrared sensors should be installed over ground that is flat and even. In a stand-alone 

configuration, the sensor should have a detection height of 3.7 meters (12 feet) or more and 

should be installed over a hard surface made of concrete or other material to prevent the 

digging of a trench beneath the lower beam. In a stand-alone installation, the lower beam 

should be no higher than 6 inches, depending on the size of the optics. Therefore, a crawling 

intruder must interrupt the beam sufficiently (typically 98-percent beam block) to cause an alarm 
 3-31 

at any location between the transmitter and receiver. Some models will not have a beam this 

low. The alternatives are to use an active infrared sensor in a complementary combination with 

another sensor that will detect a crawler or to install a hard surface beneath the sensor that is 

high enough to reduce the distance to the lower beam and, hence, allow for crawler detection. 

In locations that are susceptible to freezing, a sensor heater option is available for many 

models. The heater is typically controlled thermostatically and requires considerably more 

power than the sensor electronics. Care should be taken to size the wire appropriately for the 

electrical current requirements of the sensor heater. 

To be effective, all perimeter sensors should be installed in continuous lines of detection. For 

the active infrared sensor, sensor overlap should be provided. The layout must be designed in 

such a manner to prevent gaps large enough for an intruder to maneuver around the beams of 

adjacent sectors. One method of intersecting sectors is to “basket weave” the active infrared 

sensors. An intersection can also be made by overlapping the beams in parallel, such that the 

beams of each sector pass very close to the transmitter or receiver column of the adjacent 

sector. A transmitter should face the adjacent transmitter and the receiver should face the 

adjacent receiver to avoid interference. Figure 25 illustrates these two methods. 

Figure 25: Active infrared sector intersection methods. 
 3-32 

Another method, a variant of the parallel method, is to mount the transmitter and receiver 

columns from adjacent sectors next to each other, leaving no gap large enough to allow an 

intruder to pass between them. Once installed, the active infrared sensor modules must be 

aligned to their matching receiver or transmitter in the opposite column. Poor alignment can 

result in a poorly received infrared signal level. This, in turn, can result in increased nuisance 

alarms. 

3.4.6 Maintenance 

Active infrared sensors should be maintained in accordance with the manufacturer’s 

recommendations. Routine maintenance should involve a physical inspection of the sensor and 

the clear area where the sensor is mounted. Plant growth, debris, or anything that is unusual 

should be removed. Maintenance includes periodic cleaning of the sensor’s optics. The 

physical inspections can be combined with the scheduled testing of the sensor. However, an 

increase in nuisance alarms indicates the need for physical inspections; increased nuisance 

alarms should be investigated as soon as noted. 

Routine inspections should include the following: 

 Inspect for any weed growth and sterilize the soil or remove any growth near the sensor. 

 Inspect for and remove any debris that could cause nuisance alarms. 

 Inspect the lens or lens covers for any dirt or debris, including insects or spider webs; 

clean as needed. 

 Inspect all mechanical parts for any sign of damage or tampering. 

 Look for any areas of erosion or damage to the hard surface under the lower beam (if 

used) that could eventually increase the gap beneath the active infrared sensor’s lower 

beam. 

Any major replacement of the electronics or adjustment of the sensor should be followed by a 

performance test. All maintenance actions should be recorded. 

3.4.7 Testing 

3.4.7.1 Acceptance Testing 

When a sensor is first installed, it should be tested in order to formally “accept” the sensor as 

part of the physical protection system. Acceptance testing consists of two parts: 

(1) a physical inspection to ensure that the sensor was installed properly, as follows: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify sector intersection spacing. 

 Verify that signal and power wires are routed in conduit. 

 Verify proper power levels, both voltage and amperage. 

 Verify correct wire connections. 
 3-33 

 Perform an optical alignment on all units to verify that all modules are operational 

and oriented correctly. The method of optical alignment is specific for each 

manufacturer’s model. 

(2) a performance test to establish and document the level of performance. 

3.4.7.2 Performance Testing 

A performance test should be designed to verify the level of performance of each active infrared 

sensor through its range of intended function and should include the use of all defeat 

methodologies applicable to the system. The replacement of the electronics module, a change 

to the optical alignment, or any adjustment that could affect the unit’s sensitivity are examples of 

system changes that require performance testing. The performance test should include the use 

of the documented levels of performance from the original acceptance testing to verify that the 

sensor is still performing adequately. 

The following describes a recommended performance test for an active infrared sensor: 

(1) A performance test should include a visual inspection of the sensor and of the general 

area where the sensor is installed. Refer to section 3.4.7 “Maintenance” of this 

document to perform the recommended routine maintenance inspection. 

(2) Record all relevant processor readings. Compare to the last recorded readings, either 

from the acceptance test or the previous performance test. Each manufacturer’s model 

will have different sensor settings. Make a special note regarding any significant 

settings that may influence the detection ability or the nuisance alarm rate of the sensor. 

(3) Active infrared intrusion detection sensors can have a probability of detection for a 

walking intruder that appears to be perfect (PD = 1). This is because the sensor is a 

beam-break sensor and has no direct adjustment for sensitivity. A breaking of the 

infrared beam for the prescribed time will produce an alarm if the electronics are not 

defective. It is necessary, then, to confirm that the sensor does produce an alarm output 

that is communicated to the alarm system in response to a beam break of each beam. 

Cover each beam and verify that an alarm is produced. Do this at both columns. 

(4) Because most units employ a timing feature, it is necessary to confirm that a fast-moving 

intruder will be detected when penetration occurs. A person should penetrate the sensor 

moving as fast as possible, while avoiding the bottom beam, which sometimes has a 

faster beam-interruption time than the other beams. 

(5) The area where the sensors overlap should be tested to verify that each attempt to 

bypass the sensor under test produces an alarm on either the sector being tested or the 

adjacent sector. 

(6) The active infrared sensor can be defeated by bypassing the beams, either by crawling 

under or by aided climbing and jumping. Pay particular attention to any low places. If 

used in a stand-alone configuration, verify that the hard surface underneath the lowest 

beam is intact. Verify that attempts to crawl under the sensor are always detected at the 

location where the greatest gap exists under the lower beam. If this location cannot be 

readily identified, distribute the crawl test along the length of the sector being tested. 
 3-34 

(7) If the sensor is used as part of a complementary sensor system and the other sensor is 

intended to detect the crawler or to detect climbing approaches that use ladders or other 

aids, then that additional sensor should also be tested to verify that it functions as 

intended (by detecting what its complementary sensor does not). (This objective should 

also be part of the other sensor’s performance test plan.) 

(8) Optical alignment of an active infrared sensor is a common adjustment required of all 

models. A misaligned sensor will have an attribute of an increased number of nuisance 

alarms. If nuisance alarms are excessive, inspect for evidence of animals or debris 

present, and check the alignment signal level if available on the specific model. Also 

inspect the optics for dirt or damage. If the alarms occur at certain times of the day and 

dew or frost might be the cause, check that the heater is operational. 

If no cause for the increased nuisance alarms can be identified, perform an optical alignment. 

After alignment, slowly obscure each beam and identify the one that requires less blockage than 

the others before alarming. This will indicate that either the transmitter or the receiver module is 

defective, especially if the beam has already been aligned. 

3.4.7.3 Operability Testing 

Operability tests are simply “walk tests.” The testing individual walks through the detection zone 

of the active infrared sensor and verifies that the alarm arrived at the alarm display center. It is 

recommended that this testing be incorporated with an inspection of the perimeter security 

system. This inspection should note the status of the perimeter fence and other physical 

barriers and all physical security equipment nearby. The inspection should look for evidence 

that any component has been tampered with or damaged. Appropriate actions for repair should 

be taken if needed, and indications of tampering should be reported, investigated, and 

documented. 

3.5 Taut Wire Sensors

3.5.1 Principles of Operation 

An installation of taut wire sensors consists of multiple strands of twisted wires strung between 

dedicated posts, known as a freestanding installation (see Figure 26), or attached to an existing 

fence (see Figure 27). The twisted wires are generally made of a high-tensile strength barbed 

wire (not a farm-grade barbed wire). These wires function as a spring over a wide temperature 

range. A switch or sensor is attached to each wire and located in the middle of the wire 

spanned between two anchor posts. The distance between anchor posts can be up to 

100 meters (328 feet), depending on the type of sensor and the sensitivity required. The 

number of wires and their spacing are critical to the effectiveness of this sensor. 
 3-35 

Figure 26: A freestanding taut wire installation for environmental testing. 

Taut wire sensors will register a detection and alarm when one or more sensors sense a 

deflection of the wire(s) in a horizontal direction. This horizontal deflection is caused either by a 

certain amount of pressure applied somewhere along a wire’s length (see Figure 28) or by a 

wire being cut or broken. 

Within the categories of intrusion detection sensors, a taut wire system is a terrain-following, 

point-of-detection and visible sensor. 
 3-36 

Figure 27: A taut wire sensor system installed on an existing fence. Note the application of taut wire to the 

outriggers in this test application. 

Figure 28 A tester pushes down with moderate pressure on one of the wires of a taut wire installation. Note 

the deflection of the switch (sensor). 

3.5.2 Types of Taut Wire Systems 

The major difference between the various taut wire systems is the type of sensor/switch that is 

used to detect a deflection in a wire. The two most common switches on the market today are 

mechanical and electromechanical. The mechanical switch is a simple device whose threshold 

of detection can be adjusted only through the adjustment of tension on the individual wires. The 

electromechanical switch can control the threshold of detection through the use of software to 

adjust the detection threshold for each wire’s tension, which allows for easier adjustments for 
 3-37 

greater ease of implementation and use. Types of taut wire electromechanical switches 

available on the market include strain gauge, piezoelectric, fiber optics, and resistive rubber. 

3.5.3 Sources of Nuisance Alarms 

The primary advantage of a taut wire sensor system is that, if correctly installed and maintained, 

there are few sources of nuisance alarms. This statement should not be interpreted to mean 

that taut wire is an ideal sensor for most applications. (Refer to the “Characteristics and 

Applications” Section below.) 

One possible source of nuisance alarms, though fairly rare, is a serious ice storm. If large 

amounts of ice build up on the wires, physical damage to the system may occur. 

In some areas of the country, the facility experiences a wide variety of temperature fluctuations 

(from -20 degrees Fahrenheit (F) to 100 degrees F) over the course of a year. This large 

temperature fluctuation can change the tension of the wire, causing sensitivity concerns and 

may require additional maintenance because of the stretching and shrinking of the wire. A 

facility in this type of location may need to perform readjustments or retensioning of the wires on 

a seasonal basis to provide a uniform probability of detection. 

A highly corrosive environment, such as near the ocean, can cause increased maintenance and 

reliability concerns if the taut wire system is not purchased in stainless steel or aluminum 

versions. Also, during high winds, a large piece of heavy debris (such as heavy cardboard or a 

sheet of plywood) flying against the wires could cause a nuisance alarm. Refer to Figure 29. 

3.5.4 Characteristics and Applications 

The following list describes the characteristics and applications of taut wire fence sensors: 

 Very low nuisance alarm rate; small animals (rabbits, rodents) and weed vegetation do 

not typically cause alarms 

 Terrain-following (to a degree) 

 Not affected by most weather conditions (except for heavy ice buildup) 

 Works effectively during fog conditions 

 Installed on the outside of the inner perimeter fence as a validation of an alarm condition 

in conjunction with a different sensor type 

 Can be installed along outriggers of a fence 

 May be installed along the edge of roofs as both a barrier and a sensor 

 Can be applied in highly corrosive environments if all components are manufactured with 

stainless steel and aluminum 

 Can be mounted on an existing chain-link fence with minor modifications 
 3-38 

 Can be combined with a fence disturbance sensor as an outrigger system to detect 

climbing intrusions, while relying on the fence disturbance sensor to detect cutting 

intrusion attempts (less expensive than a full taut wire sensor installation) 

 Optimal performance when the taut wire sensor serves as part of a multisensor PIDAS 

Figure 29: Examples of sources of nuisance alarms for taut wire fencing include ice forming on the taut 

wires, flying heavy debris, or a location that experiences weather extremes—very cold winters and very hot 

summers. 

 Depending on the sensor and the intermediate and anchor post configuration, a taut wire 

system may be able to be bridged using a ladder without causing a detection. 

 Clamping and cutting the wires or slowly separating the wire to create a passable 

opening could allow an intruder access without detection (although this is not an easy 

thing to do). 

 If noncorrosive components are not used, wires and components could corrode in a 

highly corrosive environment, which could affect the friction between wires and their 

mountings, thereby decreasing the sensitivity of the system. 

 Tunneling/digging under the taut wire may be a concern if an adequate concrete curb or 

a sensor designed to detect a crawling intruder, such as a ported coax sensor, is not 

installed beneath the lowest wire. 

 If anchor and/or sensor posts are poorly installed, slight movements of the posts can 

cause a significant nuisance. 
 3-39 

 A taut wire system should not serve as the single sensor in a PIDAS. 

 A taut wire sensor can be installed on gates, but it is challenging. The use of another 

technology, such as an active infrared sensor, on a gate is much preferred. 

 As with most sensors, a taut wire system should not be installed on the outside of the 

outermost PIDAS fence, as the system could be easily bridged. 

 A taut wire system should not be installed on the inside of either PIDAS fence because 

an adversary could climb the outside of the fence, then jump down without the taut wire 

system alarming. 

3.5.5 Installation 

Manufacturer’s specifications should be followed for installation. 

Installation of a taut wire system may be freestanding (where the wires are mounted on their 

own dedicated posts), or the system may be attached to an existing sturdy fence. For a 

freestanding system, it is critical that the outer-most anchor posts for each taut wire system be 

installed with sufficient bracing to withstand the tension created by the wires. The bracing 

should not provide an advantage to an adversary attempting to climb the post to bypass the 

IDS. 

The anchor post will generally be a sturdier post than the sensor and intermediate posts in the 

system. 

The wires of the taut wire system are securely attached to each anchor post in various ways 

depending on the manufacturer. For short sectors, springs are usually incorporated at the 

anchor post to provide enough movement at the sensor to enable an alarm. 

A sensor post is installed at the midpoint of the sector length (which is usually 50 or 

100 meters (164 or 328 feet), depending on the system manufacturer). Sensor/switches will be 

mounted along this pole, and the wires are attached to these switches. 

Additional posts, referred to as intermediate posts, are installed about every 3 meters (approx. 

9.8 feet) between each anchor post and the sensor post. A slider coil the length of the post is 

installed at these locations to provide a support to, and to maintain the spacing for, the sense 

wires. The installer slides a fixing bar down between the post and the slider coil such that the 

wires remain in position but are still free-moving. 

If barbed wire is used, the installer should be certain that a barb from the barbed wire does not 

catch on any of the coils; the wire must remain “free” between the anchor post and the sensor 

post. One or more individual barbs from the barbed wire may need to be removed to prevent 

excessive friction. 

Depending on the threat facing the facility, concrete curbing may be installed beneath the 

bottom-most wire to discourage digging underneath the taut wire fence. 
 3-40 

Typical installation guidelines require approximately 100 pounds of tension on each wire. A 

typical taut wire system will alarm when 25 pounds or more of pressure is exerted on at least 

one wire. This pressure can result from a person pulling on a wire in any direction, from a wire 

being climbed on, or from a wire being cut, which releases the tension on one side of the 

sensor. 

A taut wire system is terrain-following to only a certain degree. Over the length of a taut wire 

unit, there can be no more than a total of 15 degrees of change in the elevation of the wire 

between all posts, with the wire always remaining parallel to the ground. That 15 degrees 

includes change both up and down. If there is more change in the angles than that, the friction 

between the wires and the coils holding them becomes too great, such that the wires are not 

adequately free-moving to detect an alarm condition. 

3.5.6 Testing 

3.5.6.1 Acceptance Testing 

Acceptance testing is the process that a site must go through after an installer has completed 

the installation of the sensor system but before the system is accepted and used operationally. 

Acceptance testing (for IDSs) consists of two parts: 

(1) A complete and positive performance test (see below). 

(2) Before acceptance testing, the newly installed system should be thoroughly examined to 

ensure that it has been installed according to manufacturer’s specifications and the 

detailed engineering drawings for the site-specific design/installation of the taut wire 

system. A facilities engineer will need to ascertain that commonly accepted practices 

have been followed, such as: Was the system wired correctly? Are poles installed at 

90 degrees? Are wires parallel with the ground and each other? Are voltages correct? 

3.5.6.2 Performance Testing 

Performance tests for this system should be performed on the wires on each side of a sensor 

because the lowest sensitivity of the system will be located at the furthest point away from the 

sensor post. Testing should be concentrated at or near the anchor post. Other tests can and 

should be performed at other locations along the wires to verify uniform sensitivity. However, 

testing of the wires should not be done close (approximately within 10 feet) to the sensor itself 

as damage can occur to the sensor. 

Two types of tests can be performed on the sensor without damaging the system. Each of 

these methods tests that the deflection of the wires from a person either climbing the wires or 

placing a ladder against the wires will cause an alarm. No actual cutting of the sense wires 

should be performed. 

The ladder test consists of placing a ladder against the wires and an individual climbing the 

ladder to a point where sensor activation occurs. The alarm should generally occur before the 

knees of the tester are near the top of the fence but the test should be terminated as soon as an 

alarm is received to prevent damage to the sensors. It is a good idea to provide a local alarm 

annunciation during testing to facilitate this. 
 3-41 

To test the individual wire deflection, a yard stick can be used to measure the distance that each 

wire can be moved before an alarm occurs. Providing a method to hang the yard stick from 

above the wire being tested can facilitate this. Refer to Figure 30 for an illustration of this 

measurement technique. The distance that any single wire should be able to be deflected 

before receiving an alarm is based on site-specific requirements; however, a deflection of no 

more than 3 to 4 inches should be tolerated. 

Figure 30: A hanging yardstick allows for easy measurement of the deflection possible on a taut wire 

sensor before an alarm occurs. 

For taut wire systems utilizing electromechanical devices for monitoring the wires, any software 

setting or sensitivity parameters that are adjustable in the processors should be measured or 

verified and documented. Also, any processor box located at the fence should have a tamper 

switch that is tested as part of the semi-annual performance test. 

Deflection results should be documented to be able to monitor for system changes or 

degradation over time. 

During periods of extreme cold weather, it may take some time for the mechanical sensor 

switches to return to the normal neutral position after activation. This should be considered 

when considering multiple tests of the same zone. 
 3-42 

3.5.6.3 Operability Testing 

The standard operability test for this system is simply a matter of pulling up or down on one of 

the wires of a particular sector until an alarm is received at the alarm monitoring station. 

Because of the number of sensors (i.e., wires) that make up the taut wire system, it is wise to 

provide some method of ensuring that a different wire is tested each time the test is performed. 

This ensures that, over time, all of the wires and sensors will be tested for operability. 

3.5.7 Maintenance 

Maintenance to the taut wire system is essential for consistent performance. During the weekly 

operability testing of the system, the tester should be observant of any abnormalities that may 

exist. At a minimum, the inspection should entail the following: 

 Remove any foreign objects that may have blown into or otherwise been lodged on the 

wires. 

 Remove any vegetation growing onto the wires. 

 Inspect the ground beneath the system for signs of erosion or digging by animals. 

 Inspect the condition of the slider coils, and ensure that the fixing bar is in place and is 

secure. 

 Ensure that the wires are not jammed or snagged at the slider coils or sensor post and 

that no barbs are within 2 to 3 inches of the slider coils. 

 Inspect the condition of the sensors to ensure that components are not cracked or 

damaged and that the wires are securely attached. 

 Inspect wires for condition, spacing, and tautness. 

 Perform any other inspections or maintenance specified by the manufacturer. 

 At least once per year or whenever physical inspection warrants, the tautness of the 

wires should be verified using a dynamometer to ensure tension is within manufacturer’s 

specifications. 

3.6 Fence Disturbance Sensors

3.6.1 Principles of Operation 

A fence disturbance sensor is designed to be mounted on a chain-link fence to detect 

disturbances of the fence, such as the noises or motions generated when an intruder attempts 

to climb over or cut through the fence fabric. (Refer to Figure 31.) 
 3-43 

Figure 31: This diagram illustrates the deflection caused by climbing on chain-link fence fabric; this 

disturbance of the fabric is one of the ways that fence disturbance sensors work. 

A climber generates two types of disturbance while climbing the chain-link fabric: a slow, 

low-frequency motion of the fabric movement and a higher frequency, impulsive shock or noise 

caused by pieces of the fence striking or rubbing against each other. Cutting the fence fabric 

also generates an impulsive shock. Some types of fence disturbance sensors have dual 

processors so that they can distinguish between the slow, low-frequency motion of the fabric 

and the high-frequency shock noises. 

When someone or something causes a significant disturbance to a fence, a switch will activate 

or a signal will cross a threshold, which is considered to be an event. 

Most fence disturbance sensors require a specified minimum number of events to occur within a 

specified time in order to generate an alarm condition. For example, a facility could specify that 

an event must be detected five times within half a minute before an alarm is reported. The 

decision for these parameters should be driven by the threat, physical protection program goals 

and the physical characteristics of the fence (i.e., height and wire mesh size). A lower number 

of required events would increase the probability of detection but increase the nuisance alarm 

rate as well. Requiring a higher number of events to generate an alarm would cause the 

opposite (i.e., a lower probability of detection but improved (lower) nuisance alarm rate). 

The actual number of events over a specific period of time required to cause an alarm at a 

particular facility is generally considered sensitive information since knowledge of these 

parameters would give an adversary the advantage needed to possibly defeat that system. 
 3-44 

3.6.2 Types of Fence Disturbance Sensors 

3.6.2.1 Mechanical Fence Sensors 

Mechanical fence sensors operate on the principle that fence movement will cause a switch to 

open or will close a set of contacts. One of two approaches is generally used. First, mercury 

switches are used to detect side-to-side movement or tilting of the fence and signal processors 

employ count and time criteria to differentiate between intrusions and nuisance indications. The 

second method employs a mass on a set of contacts. The system detects impulsive fence 

movements of sufficient magnitude to cause the mass to move off the contacts momentarily. 

Generally, this method also uses count and time criteria to generate an alarm indication. Such 

sensors are positioned on the fence at regular intervals. 

3.6.2.2 Electromechanical Fence Sensors 

Electromechanical fence sensors employ individual point transducers to detect fence motion. 

The point transducers produce an analog signal instead of a switch closure and use an 

electronic signal processor to extract alarm information from the signal. Like mechanical fence 

sensors, these sensors are positioned on the fence at regular intervals. For high-security 

applications, the transducers are placed on every pole or on the fence fabric itself between each 

pair of poles. 

Two types of electromechanical transducers are used: geophone and piezoelectric. The 

principles of operation for each type are given below. 

3.6.2.2.1 Geophones

A geophone transducer uses the principle of a conducting loop moving in a fixed magnetic field 

to generate a voltage. Either the coil or the magnets are mounted on a spring structure so that, 

when the body of the geophone moves, there is relative motion between the coils and the 

magnets, causing a voltage output. 

Geophones are sensitive to movement along one axis only, and thus they are mounted on the 

fence so that they are sensitive to the vertical movements of the fence. This orientation helps to 

eliminate nuisance alarms caused by wind-induced fence movements. 

3.6.2.2.2 Piezoelectric Sensors

Piezoelectric transducers detect fence motion by employing crystals that exhibit the 

piezoelectric effect: when the crystal is deformed, a voltage appears across the crystal. The 

crystals are mounted in a housing in such a way that fence motions are detected. The 

transducers are sensitive along a major axis and are generally mounted to be most sensitive to 

vertical fence motion. 

3.6.2.3 Strain-Sensitive Cable 

Strain-sensitive cable is a transducer that is uniformly sensitive along its entire length. It is 

specially designed to produce an output voltage when the cable is moved. An electric cable 

uses a polarized dielectric to become microphonic. Another cable type uses special 
 3-45 

construction to enhance voltage output caused by the triboelectric effect. The triboelectric effect 

is an electrical phenomenon in which certain materials become electrically charged by friction 

after being rubbed together. A third type resembles a distributed geophone with magnetic 

material surrounding sense wires in one cable. Each cable type is fastened directly to the fence 

using wire ties so movement of the fence fabric is coupled directly to the transducer cable. 

Figure 32 shows a typical installation of strain-sensitive cable. 

Figure 32: Typical installation of strain-sensitive cable. 

3.6.2.4 Fiber-Optic Cable 

Fiber optics is the class of optical technology that uses strands of optically pure glass as thin as 

a human hair to carry digital information over long distances. A light source, such as a lightemitting diode (LED) or laser diode, is coupled to one end of the fiber, while a receiver (such as 

a photo transistor or similar device) is coupled to the other end of the fiber. The two major 

categories of fiber-optic sensors are continuity sensors and microbending sensors. Major 

advantages of fiber-optic cable include immunity to radio and electromagnetic interference and 

durability in conditions of changing temperature and humidity. 

Since the fiber does not have to be straight to reflect the light from one end to the other, it can 

be installed in various configurations on a fence or be buried in the ground to sense a 

disturbance. The light diffraction (speckle) pattern and the light intensity at the end of the fiber 

are a function of the shape of the fiber over its entire length. Motion, vibration, or pressure of 

the fiber induces modal differences causing a phase shift in the light. Sophisticated processors 

can detect these phase shifts or minute changes in the light patterns being sent down the cable. 

These changes can be characterized by the processor as those being produced by someone 

cutting or climbing the fence, and when the right criteria are met (as set in the parameters of the 

processor), an alarm will be generated. 

Some processors have the capability of allowing long lengths (up to tens of kilometers) of 

nonsensing cable (single-mode fiber) to be placed between it and a length of sensing cable 
 3-46 

(multimode fiber). This allows the processor(s) to be located in a central location a long 

distance from the fence being protected. 

3.6.3 Sources of Nuisance Alarms 

The tension of the fence fabric and the general condition of the fence can affect both the 

performance and the number of nuisance alarms that will be experienced. Tight fabric 

enhances the transmission of noises along the fence, making the slight noises caused by a 

climbing or cutting intruder easier to distinguish. On the other hand, loose fabric may allow the 

fabric to flap against the post or other fence parts causing increased noise and increased 

nuisance alarms. 

The rate of nuisance alarms for fence disturbance sensors can be affected by many factors 

including rain, hail, melting ice, wind, wind-blown debris, lightning, and the physical condition of 

the fence on which they are mounted. The magnitude of the effects of each of these sources 

depends on the type of sensor, the installation method, sensor maintenance practices, and the 

adjusted sensitivity or other settings. 

It is also important that some fence disturbance sensors are not used near an electrical 

high-power line. Radios may also have an impact on the geophonic type of fence disturbance 

sensors. Immunity to these sources is one advantage of using fiber-optic technologies. 

Since fiber-optic cable senses vibrations, nuisance alarm sources can be similar to those of 

seismic sensors. Anything causing a noise or vibration in the fence structure or fabric will likely 

be detected by the sensor. New digital processing algorithms incorporated into most 

processors have some capabilities to filter out extraneous noise such as that produced by wind 

or other vibrations. So, as with other fence disturbance sensors, the general condition of the 

fence is very important for the proper performance of this technology. 

3.6.4 Characteristics and Applications 

The following describes the characteristics and applications of fence disturbance sensors: 

 Some cable types will provide the location along the fence disturbance sensor at which a 

detection occurred, which allows a quicker and more accurate assessment of an alarm. 

 Most fence disturbance sensors are relatively inexpensive to purchase and inexpensive 

to install. This is particularly true since most facilities already have some sort of fence 

installed as a boundary marker. 

 A fence disturbance type of sensor can be applied with excellent reliability to protect an 

asset located indoors. One example of this is a sensor applied to a cage that is built 

around the asset. 

 An adversary who climbs or cuts a fence very slowly may be able to spoof a fence 

disturbance sensor; however, this can be much harder to do than it sounds. This 

scenario may be exacerbated if the adversary knows the event count and time 

constraints for alarm generation. 

 A typical stand-alone fence disturbance sensor installation can be bridged over or 

trenched under. 
 3-47 

 A fence disturbance sensor should not be used on the outer fence or as a facility’s only 

line of detection. 

 Typical rigid conduit installed on the fence will expand and contract with temperature 

changes, which will cause nuisance alarms. 

 Fence disturbance sensors (except for fiber-optic technologies) should not be used near 

a high-power line. Radios may also have an impact on the geophonic type of fence 

disturbance sensors. Careful testing and evaluation should be conducted at the site 

before installation of the sensors to determine the frequencies and wattages that may be 

problematic. 

3.6.5 Installation Criteria 

It is possible to install a fence disturbance sensor on an existing chain-link fence; however, 

there is generally too much “noise” if the fence was not installed with the original goal of 

supporting such a sensor, and many adjustments will be required over time to achieve 

acceptable sensor performance. The following guidelines are suggested for preparing and 

evaluating a security fence for compatibility with fence-mounted intrusion detection sensors 

designed to sense motion, displacement, and/or acceleration forces resulting from an intrusion 

attempt: 

 The fabric of the fence should be located on the unprotected side of the posts. 

 The fence fabric should be stretched to allow not more than 2.5 inches of deflection 

when a 30-pound perpendicular load is applied at the center of the panel. 

 The fence posts should not deflect more than 1.9 centimeters (.75 inches) when a 50-

pound perpendicular load is applied at a height of 1.5 meters (5 feet) above the base of 

the post. 

 The fence fabric should not be embedded in a concrete or otherwise solid sill. This will 

preclude later tightening of the fabric if necessary. 

 The fence should not have a top rail. Top rails reduce sensor performance while aiding 

the climbing adversary. However, the fence should have a bottom rail. 

 The fence should not have outriggers that tend to be noisy and cause unwanted 

nuisance alarms. 

 Tension wires should be used to provide for the stabilization of the fence fabric. 

 The top of the fence posts should be approximately 4 inches below the top of the fabric 

to prevent an adversary from using the post as a bridging aid or leaning a ladder against 

it. 

 Wire ties should be used to secure the fence fabric to the structural members of the 

fence (i.e., posts, braces, or tension wires). The wire ties should be 9-gauge or thicker 

zinc-coated steel. Refer to Figure 33. 

 The fence fabric should be secured with wire ties approximately every 12 inches. 
 3-48 

 The wire ties should form a 540-degree tightened loop that is secure enough to prevent 

movement between the fence fabric and the wire tie. 

Figure 33: Example of security fence wire ties. 

Note that some fence disturbance sensors can accept input from an anemometer (windspeed 

indicator) so that the processing of events can be changed when windspeed exceeds a certain 

speed. Care should be taken when using this type of system as it can provide an automatically 

increasing attenuation of the sensitivity of the system as the wind increases. The wind can 

increase to a point where the sensor is no longer providing intrusion detection, unbeknownst to 

the operator. It is preferable to allow the operator to put the sensor into access if the nuisance 

alarms increase to an intolerable level and compensatory measures can be implemented as 

necessary. 

Certain fence disturbance sensors will allow the sensitivity of each meter, or so, of the cable to 

be adjusted independently along the length of the cable to compensate for variations in the 

fence such as corners, tension posts, and gates. This flexibility also allows zones to be user 

defined in the software of the processor, potentially reducing the number of processors 

necessary. 

Signs should not be mounted on a fence that supports a fence disturbance sensor. During 

windy conditions, the sign is likely to be a source of noise or provide a larger surface and 

thereby increase the fence movement and noise and, consequently, increase the number of 

nuisance alarms. If a sign must be mounted on a fence supporting a fence disturbance sensor, 

it should be attached with twisted metallic wire ties to secure the sign from rattling. 

If chains are used anywhere along a fence that supports a fence disturbance sensor, such as to 

secure a gate, the chain should be rubber coated and as short as possible. 

Inside protected 

area 

Outside 

protected area 
 3-49 

Tree branches, weeds, and other objects that could cause mechanical disturbance of the fence 

should be removed. Gates, barbed wire, and outriggers (when used) should be mechanically 

sound and, where appropriate, firmly attached to other parts of the fence. Such precautions 

prevent clatter or mechanical disturbances within the fence itself. 

3.6.6 Testing 

Three types of testing need to be performed during the life of a sensor: acceptance testing, 

performance testing, and operability testing. 

3.6.6.1 Acceptance Testing 

When a sensor is first installed, it should be tested in order to formally “accept” the sensor as 

part of the physical protection system. Acceptance testing consists of two parts: 

(1) A physical inspection to ensure that the sensor is installed properly, as follows: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify sector intersection spacing. 

 Verify that signal and power wires are routed in conduit. 

 Verify proper power levels, both voltage and amperage. 

 Verify correct wire connections. 

(2) A performance test to establish and document the level of performance (see next 

section). 

3.6.6.2 Performance Testing 

Performance tests should be designed to verify the level of performance of the sensor through 

its range of intended function. Fence disturbance sensors are designed to detect an adversary 

attempting to climb over or cut through the fence. 

The following are examples of when a performance test should be conducted. 

 A processor is replaced. 

 Sensor cables are replaced or repaired. 

 An adjustment that can affect sensitivity is made to the processor parameters. 

 Configuration of the installed sensor cables is changed. 

 There has been a change to the sensor or in the near vicinity of the sensor that might 

affect the detection sensitivity. 

This test should include a visual inspection of the sensor and of the general area where the 

sensor is installed. The testers should refer to the maintenance section and perform the 

required routine maintenance. 
 3-50 

All relevant processor readings and parameter settings that can affect the detection capabilities 

or the nuisance alarm rate should be recorded. Each manufacturer will have different sensor 

settings. The test should involve comparison of the current readings to the last recorded 

readings to ensure that they fall within the manufacturer’s specifications. 

To test the detection capabilities against a climb, the tester will actually climb the fence fabric. 

To preserve the integrity of the fence fabric, test devices are available that provide a consistent, 

simulated cut disturbance to the fence without damaging the fence fabric. (Refer to Figure 34.) 

Figure 34: An example of a fence-cut simulation tool in use. 

Sufficient testing should be performed to provide the probability of sensing (PS) at the 

confidence level defined for the facility. For example, a “30/30” test methodology and binomial 

distribution may be used to yield a 90-percent PS performance at a 95-percent confidence level. 

Using this methodology, if the sensor alarms 30 times when subjected to 30 attempted 

intrusions, the PS value is equal to 0.90 at a 95-percent confidence level based on the values 

derived from a binomial reliability table. 

Performance testing of fence disturbance sensors should include the following procedures. 

Performance tests should be conducted at 30 equidistant points along the length of the 

detection zone/sector. One or more test trials should be performed for each of the 30 test 

locations. Particular attention should be directed to locations where sensitivity might vary if the 

installation configuration varies from the norm, such as at corners, sector overlaps, or where 

fence structure is more significant. 

3.6.6.2.1 Procedure 1: Conduct Climb Tests

Conduct 30 climb tests within the detection zone/sector to verify PS = 0.90 at a 95-percent 

confidence level. 

Each sector should be tested 30 times at points equidistant along the length of the sector. For 

this procedure, the adversary test subject should attempt to climb the fabric from the outer 

(unprotected) side of the fence. (Refer to Figure 35.) If climb testing of the fence is required 

from the inner side, do not use the fence support posts to aid in climbing. A failure is recorded if 
 3-51 

the adversary test subject can reach the top of the fence and start to go over without an alarm 

being generated. 

Figure 35: Test climbing the fence from the outer (unprotected) side. 

3.6.6.2.2 Procedure 2: Conduct Simulated Cut Tests

Using the simulated cut device, conduct 30 simulated cut tests within the detection zone/sector 

to verify PS = 0.90 at a 95-percent confidence level. 

Each sector should be tested 30 times at points equidistant along the length of the sector. For 

each trial, use the cut simulation tool to strike the fence (releasing the plunger from the middle 

notch) X1 times at a point either 12 inches from the ground, 12 inches from the top of the fence, 

or at a point in the middle of the fence fabric. Ensure that the test device is firmly pressed 

against the fabric when releasing the plunger. The strikes should be at approximately X second 

intervals. A failure shall be recorded if the tester can strike the fence X times within the 

designated timeframe without generating an alarm. 

3.6.6.2.3 Procedure 3: Verify Processor Enclosure Tamper Alarm

Test the tamper alarm of the processor enclosure by slowly opening the door to the enclosure. 

A failure shall be recorded if an alarm is not received or if the cover can be opened more than 1 

inch before an alarm is received. 

 

1 X = The numbers for the amount of times needed to strike the fence and the required time interval to generate an 

alarm which are determined by the site and are usually classified. 
 3-52 

3.6.6.2.4 Resettling Time

When following the performance test procedures, allow sufficient time for the system under test 

to stabilize or reset between each individual test trial. 

3.6.6.2.5 Verification of Failure to Alarm

If an alarm is not received for a given trial, two more attempts may be made at the same 

location using the same test method. The trial should be considered a valid detection and 

testing can proceed only if both of the additional trials result in successful alarms. If either 

additional trial results in a failure, testing of the system should cease and corrective action 

should be taken. Following required maintenance or recalibration, the complete performance 

test procedure should be conducted again using the same test methodology at all test locations 

(if possible) to verify acceptable sensor performance. If sensing performance does not meet 

requirements after all reasonable corrective actions have been attempted, the test should be 

annotated as a failure. 

3.6.6.3 Operability Testing 

The operability test is conducted by causing a disturbance to the fence fabric within the zone to 

be tested. The disturbance can be caused by striking the fence with some object or simply 

shaking the fence until an alarm is received at the alarm monitoring station. The striking or 

shaking force to be exerted during the operability test is usually outlined in manufacturer’s 

specifications and is derived from a reasonable representation of the force that the system 

would encounter and should detect if a human were attempting to circumvent the system by 

climbing or cutting. 

If no alarm is received, a maintenance request should be immediately generated and 

implementation of compensatory measures should be considered based on site-specific 

requirements. 

3.6.7 Maintenance 

At least twice a year and after any major storms, each section of a fence disturbance sensor 

system should be carefully examined to make certain that no parts of the sensor system have 

become loose or the integrity of the fence has not been compromised. The inspection should 

include the following: 

 Ensure that wire ties for the sensor cable have not broken or become loose. 

 Ensure that all fence fabric wire ties remain tight and are securely attached to the fence 

structure. 

 Inspect for any debris that has collected against the fence and remove this debris. 

 Inspect any signs that may be mounted on the fence fabric and ensure that they are 

securely fastened. 

 Ensure that any splices or terminations in the sensor cable remain sealed and securely 

attached to the fence. 
 4-1 

4. INTERIOR INTRUSION DETECTION SENSORS 

4.1 Balanced Magnetic Switch

4.1.1 Principles of Operation 

The magnetic switch is the most ubiquitous security device in the world, used for both door and 

window protection. (Refer to Figure 36). It consists of a magnet, which is installed on a door or 

window, and a switch unit, which is installed on the frame. When the door or window is in the 

closed position, the created circuit is closed; when the door or window is opened, the circuit is 

open, which causes an alarm to be initiated. 

Figure 36: An example of the application of a magnetic switch for door protection. 

At a cost of approximately $10, the simple magnetic switch device is used in most residential 

and small business security systems. Unfortunately, little knowledge is required to defeat 

(bypass or spoof) a simple magnetic switch. In response, the balanced magnetic switch (BMS) 

was developed more than 30 years ago. The BMS requires a great deal more skill to defeat 

than a simple magnetic switch. 
 4-2 

A BMS employs a magnet in both the switch and magnet units. (Refer to Figure 37). The 

switch unit, which contains a magnetic reed switch, a bias magnet, and tamper/supervisory 

circuitry, is mounted on the stationary part of the door or window unit. The component 

containing the larger permanent magnet is mounted on the movable part of the door or window, 

adjacent to the switch unit installed on the frame when the door is closed. 

Figure 37: A schematic of a simple versus balanced magnetic switch.

With the door or window closed, the magnets are adjusted to create a magnetic loop, causing 

the reed switch to experience a magnetic field of essentially zero. When the door or window is 

opened and the magnetic field is removed, the contacts will separate and trigger an alarm 

indicating a security breach. In some models, this magnetic field is accomplished by adjusting 

the bias magnet; in other models the adjustment is made by varying the position of the magnetic 

unit with respect to the switch unit. 

Any action that causes the magnetic field to become unbalanced, such as opening the door or 

window, results in the transfer of the reed switch to the “closed” position and an alarm output. 

The same result is obtained if an external magnet is brought into the vicinity of the BMS, thus 

changing the magnetic field. 

A newer BMS codes multiple magnets in each unit; thus, each BMS is matched and the defeat 

of the BMS is nearly impossible. However, fixing a switch in a BMS that has a coded 

configuration requires that the BMS be completely replaced with another matched pair. 
 4-3 

A BMS is a passive, visible, point-detection sensor. 

4.1.2 Types of Balanced Magnetic Switch Sensors 

BMS sensors have a variety of designs. Some use multiple magnets; some have internal 

electromagnets for self-testing. Manufacturers have reduced the vulnerability of magnetic 

switches to external magnetic fields through the following measures: 

 Using multiple magnets, various magnetic orientations, and magnetic shielding, such as 

Mumetal® 

 Creating standoff distances 

 Adding magnetic tamper indicators 

The newest switches on the market have very narrowly defined magnetic field paths, making 

them almost immune to external magnets. All provide a high level of protection for access 

points such as windows and doors. The type of BMS a facility chooses should be based on 

providing reliable functionality within the environment and the goals of the physical protection 

program. 

4.1.3 Sources of Nuisance Alarms 

BMS sensors are very reliable when installed correctly on a properly installed door with 

hardware that is in good condition. Nuisance alarms are almost never caused by the BMS 

alone. 

Most nuisance alarms generated by a BMS can be attributed to the poor condition of the door or 

its hardware. Most common nuisance alarms are caused by a worn or out-of-adjustment latch 

that occurs because of excessive door movement or play. Nuisance alarms can also be caused 

by excessively worn door hinges or an improperly installed BMS that causes misalignment of 

the switch unit and magnet unit. 

When a BMS is used on large rollup doors, nuisance alarms are usually caused by slight 

misalignment of the doors. It is difficult over time to keep this type of door maintained in 

alignment for proper sensor operation. Extreme weather conditions that cause excessive 

movement of a door, window, or access portal can also increase the nuisance alarm rate of a 

BMS. 

4.1.4 Installation Criteria 

The switch assembly of a balanced magnetic sensor is mounted on the inside of the fixed 

surface and the magnetic assembly is mounted near the top of the movable surface near the 

edge that is on the opposite side of the hinge. This mounting allows for maximum detection of 

movement. 

A BMS should always be installed on the secure side of the door. 

If the BMS is installed on a recessed door or outward opening door, a spacer will be needed to 

line up the switch and magnet units. If the door frame is steel, a nonferrous (aluminum or 
 4-4 

plexiglass) spacer should be installed between the door frame and the switch unit to prevent 

interference with switch operation. Likewise, if the magnet is installed directly on a steel door, it 

should have the same type of spacer. A spacer made from 1⁄2-inch-thick plexiglass has worked 

well in many installations. Some manufacturers state that their switch compensates for the 

effects of steel. It is best to consult the manufacturer to verify the need for a spacer. 

The wiring from the BMS should be protected. Installing the wiring in a conduit from the sensor 

switch enclosure all the way to the alarm data-gathering or multiplexer panel will provide 

protection for the alarm wiring. Materials with high magnetic permeability, such as Mumetal®, 

are preferable for the shielding. However, steel can also be used. 

Sensor electronics enclosures should have tamper switches. Line supervision is the means for 

monitoring the communication link between a sensor and the alarm control center. Use of 

supervised lines between the sensor and host alarm system, as well as continuously monitored 

sensor tamper switches, will help protect against adversary attacks on communication links and 

sensor electronics enclosures. 

4.1.5 Characteristics and Applications 

A BMS is passive and visible and detects boundary penetration such as a door or window being 

opened. These switches are manufactured in different sizes and shapes and achieve different 

performance levels, depending on the manufacturer and the model. 

A BMS is a mature technology that is subject to few (if any) nuisance alarms, provided that the 

door, door frame, and door hardware are in good condition and that the BMS was installed 

properly. 

An externally introduced magnetic field has the possibility of defeating a BMS. BMS sensors 

with multiple magnets and reed switches will be much more difficult to defeat by this method. If 

a door magnet can be removed without detection, it may be possible to compromise the BMS. 

These sensors provide protection only if the intruder opens the door or window for entry. If the 

intruder cuts through the door, cuts through the wall next to the door, or breaks the window 

pane, the BMS will be bypassed. Consideration should be given to bolstering the resistance to 

adversary penetration of these potential pathways. 

High-voltage discharges from lightning, power surges, or stun guns can permanently weld reed 

switch magnetic contacts in a failed (closed) position, making the system useless when it is 

armed. If the metal contacts are welded shut, it will indicate a secure state even when the 

system is breached. 

4.1.6 Testing 

A regular program of testing sensors is imperative for maintaining them in optimal operating 

order. 

4.1.6.1 Acceptance Testing 

When a BMS sensor is first installed, it should be tested in order to formally “accept” the sensor 

as part of the physical protection system. Acceptance testing consists of two parts: 
 4-5 

(1) A physical inspection to ensure that the sensor is installed properly consists of the 

following: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify that signal and power wires are routed in the conduit. 

 Verify proper power levels (voltage and amperage). 

 Verify correct wire connections. 

(2) A performance test to establish and document the level of performance (see next 

section). 

4.1.6.2 Performance Testing 

If a BMS has had an unexplained number of nuisance alarms or if the BMS has ever failed to 

generate an alarm during a daily walkthrough test, troubleshooting and/or repair will be required; 

after this repair, a formal performance test should be run. Also, operation of the sensor tamper 

and communication to the alarm stations are verified during testing. 

Three basic tests constitute a performance test for a BMS: 

(1) Evaluate the response of the switch when an externally introduced magnetic field is 

produced via a foreign magnet during testing. (Refer to Figure 38.) 

(2) Establish that the BMS detects a door opening within a specified distance. A commonly 

used requirement is that a BMS shall generate an alarm when the leading edge of the 

door has been moved 1 inch or more from the fully closed position. 

(3) Establish that the BMS does not detect a door opening within a smaller specified 

distance. A commonly used requirement is that a BMS shall not initiate an alarm for 

door movement of 1⁄2 inch or less. The importance of the condition of the door and its 

associated hardware cannot be overemphasized. If the door is not properly installed 

and maintained, the BMS effectiveness will be degraded. 

The history of nuisance alarms and false alarms should be reviewed at this time as well. 

Establishing specific values for false alarm rates helps the operator determine when a sensor 

should be reported to maintenance personnel. 

4.1.6.3 Operability Testing 

The objective of the operability test is to verify that the sensor is operational and that the correct 

alarm signal is received and displayed at the alarm stations. 

The BMS operational test is simple and is performed by opening the door and verifying with the 

alarm station operator that an alarm was received at that particular door location. Then another 

test is conducted to verify with the operator that the sensor returns to the secure state and 

remains secure when the door is closed, latched, and pushed back and forth, given that there is 

some play in the latch. 
 4-6 

Figure 38: Demonstration of introducing an external magnetic field to a BMS. Note that this procedure 

is much more difficult to accomplish than the photos would suggest. 

The door hardware should be in good condition. The door should open and close smoothly 

without rubbing or scraping on the door frame. It should latch easily and the amount of play in 

the latch should be minimal. 

In addition to scheduled operability tests, operability testing should be performed when a 

protected location is placed into a secure condition from an unsecure condition (i.e., entrances 

locked and alarms reactivated). 

4.1.7 Maintenance 

At a minimum, maintenance of a BMS should be performed every 6 months. The following 

should be verified during maintenance: 

 Verify tamper operation by accessing electronics enclosures and disconnecting 

communicating links of the sensors and through successful communication to the alarms 

stations. 

 Verify tamper operation or alarm when a foreign magnetic field is introduced to the 

sensor. 

 Verify that an alarm occurs within a specific door movement distance, which is typically 

before the leading edge of the door has moved 1 inch. 
 4-7 

 Verify that no alarms occur during any slight movement of the door when it is latched. 

 Verify acceptable conditions of electrical power and communication lines. 

4.2 Interior Microwave Sensors

4.2.1 Principles of Operation 

Interior microwave sensors are active volumetric sensors and are typically monostatic, 

employing a single antenna for both the transmit and receive functions; all components are 

enclosed in a single housing. (Refer to Figure 39.) Microwave sensors emit an energy field. 

Motion within an area protected by a microwave will cause changes to the microwave energy, 

and these changes are a type of Doppler frequency shift. A person or other object moving 

within the microwave energy field will cause minute changes in the frequency of the microwave. 

As the sensor “knows” the frequency at which it is transmitting, when it receives reflected 

energy at a slightly different frequency, it will process the difference between the frequencies. 

An alarm will be generated if the frequency difference exceeds a preset threshold. 

Microwave sensors typically operate in the X band radiofrequency region (7 to 11 gigahertz) 

with low power output that is approximately 5 to 10 milliwatts. Figure 40 illustrates typical 

sensor coverage patterns. The size and shape of this pattern can vary significantly, depending 

on the characteristics and configuration of the microwave antenna used in the sensor design, 

although most interior monostatic microwave sensors have a detection pattern that ranges from 

approximately 9 meters (approx. 29.5 feet) up to 30 meters (approx. 98.4 feet) in length. The 

shape of the detection zone is governed by the design of the antenna and is roughly similar to 

an elongated balloon or a cigar. The antenna is usually a microwave horn but may be a printed 

circuit planar or phased-array antenna. 

Figure 39: A common interior microwave antenna propagation pattern. 
 4-8 

Figure 40: Examples of different microwave antenna propagation patterns; the half and full envelopes 

indicate half-power and full-power settings. 

Optimal detection for microwave sensors is achieved when the target is moving toward or away 

from the sensor—not across the detection zone. Therefore, placement of microwave sensors 

should be such that the adversary will be necessarily forced to move towards or away from the 

sensor to accomplish the adversary’s objective. 

4.2.2 Types of Interior Microwave Sensors 

The two basic types of microwave sensors are monostatic sensors, which have the transmitter 

and receiver encased within a single housing unit, and bistatic sensors, in which the transmitter 

and receiver are two separate units creating a detection zone between them. A bistatic system 

can cover a larger area and would typically be used if more than one sensor is required for the 

area being covered, but is more commonly applied in exterior applications. 

4.2.3 Sources of Nuisance Alarms 

Because of the high frequencies of microwave sensors, the signal/sensor is not affected by 

moving air, changes in temperature, or humidity. However, the high frequency allows the signal 

to pass through standard walls, glass, sheetrock and wood, which can cause nuisance alarms 

to be generated by movement adjacent to, but outside, the detection area. If a microwave 

sensor is installed in a room made from light construction materials and the detection area of 

that microwave is larger than the room, nuisance alarms will occur because of movement 
 4-9 

outside the room. The structural materials and the thickness that a particular microwave can 

penetrate will vary, based on the device’s manufacturer, model, and frequency. (See Figure 

41.) 

Figure 41: A microwave sensor can trigger nuisance alarms because of its ability to transmit through some 

light-weight construction materials. 

Nuisance alarms can be generated by fans, rodents, pets, or equipment. A fan that is not 

located in the room of primary detection is also a possible source. If a fan is located within a 

ventilation duct, reflections from the moving fan blades can be detected by microwave energy 

traveling through the duct. Another source of nuisance alarms for microwaves is plastic 

drainpipes located behind dry wall. Water draining through the pipes can cause alarms. 

Some microwave sensors can be triggered by fluorescent lights. The gas within fluorescent 

lights is a reflector of microwave energy when ionized. The light actually flickers at the power 

line frequency, which the sensor perceives as motion. If nearby microwave sensors generate 

nuisance alarms, a metallic screen mesh (also known as a Faraday cage) can be installed over 

the lights to prevent the microwave energy from passing through. 

Electromagnetic sources close to the microwave frequency are another possibility. In fact, if 

more than one microwave sensor is installed in the same area, they can potentially interfere 

with each other and cause nuisance alarms. Fortunately, microwave sensors are available that 

allow the user to select from several different frequencies. More than one microwave in the 

same area will require different frequencies. 

Finally, signals reflected off metal objects, such as filing cabinets, trash cans, and electrical 

boxes, can “extend” sensor coverage to areas not intended to be covered, thus creating the 

potential for nuisance alarms. 
 4-10 

4.2.4 Characteristics and Applications 

Microwave sensors are most sensitive and effective when installed so that an adversary would 

necessarily walk toward or away from the sensor. 

Microwave sensors can be used to effectively monitor interior confined spaces such as vaults, 

special storage areas, hallways, and service passageways. They can also serve as an early 

warning alert of intruders approaching a door or wall. In situations where a well-defined area of 

coverage is needed, the use of monostatic microwave sensors is appropriate. 

To further enhance detection, a facility can install a complementary sensor, such as a passive 

infrared (PIR) sensor. (A PIR sensor is considered to be complementary to a microwave sensor 

because a PIR senses best when an adversary moves across the zone of detection, unlike the 

microwave.) The use of a complementary system provides a second line of defense and 

provides security personnel with additional information to help them accurately assess an alarm 

and discriminate actual or potential penetrations from nuisance events. 

Microwave sensors are least sensitive if installed such that an adversary would be able to limit 

his or her movements to paths across the detection pattern. 

The special properties of microwave beams allow them to penetrate most types of surfaces 

(metal is not one of them). Because of this, it is possible for a microwave to detect motion in an 

area where detection is not desirable and not detect motion where it is desirable. For example, 

a large metal filing cabinet in the area of detection will shield the area behind it. Objects such 

as these create “dead zones,” areas where the sensor cannot detect motion, thereby creating a 

hiding place for a potential adversary. On the other hand, because the beam can penetrate 

walls, the sensor may detect motion behind a wall in another room. 

As microwave sensors are extremely sensitive to motion, they are also prone to nuisance 

alarms. Objects being moved by air currents generated by the heating, ventilation, and air 

conditioning (HVAC) or fans may trigger alarms. Even fluorescent lighting, which emits 

detectable light particles, may trigger a false alarm. 

Since microwave sensors operate in the high-frequency spectrum (X band), close association or 

proximity to other high-frequency signals can adversely affect their detection reliability. Areas 

that contain strong emitters of electric fields (radio transmitters) or magnetic fields (large electric 

motors or generators) can affect the ability of microwave sensors to function properly and 

should be avoided or compensated for by distinct signal separation or shielding. Self-generated 

signal reflection is a common problem caused by improper placement or mounting. Positioning 

the sensor externally and parallel to the wall rather than embedding it within the wall will aid in 

avoiding this problem. 

Very slow movement by an intruder is harder for a microwave sensor to detect, though to 

actually defeat a microwave sensor is not easy. The speed required to bypass a sensor will 

depend on its make and model. Testing in the past has shown that some microwave sensors 

will still have some sensitivity against intruders moving at speeds as slow as 1 inch per second. 

The microwave sensor will detect any swaying of the body, including movement of the head, 

arms, or legs. For a successful defeat, an intruder will be required to be inside the detection 

area for a lengthy period to allow the time necessary to move this slowly and avoid detection, 

which thereby increases the chances that the intruder will be noticed. 
 4-11 

Circumferential motion in a perfect arc, with no effective motion toward or away from the sensor, 

will not produce a Doppler shift, and hence, no detection will occur. This is, however, a very 

difficult movement for an intruder to accomplish correctly and subsequently avoid detection. 

The three graphs in Figure 42 show the differences between the detection pattern shape and 

size with respect to test subject direction of movement into an area that is sensored by a 

microwave. The left graph shows the maximum detection pattern with the test subject walking 

directly toward the sensor. The right shows a small decrease in detection pattern size with walk 

testing parallel to the sensor center line. The top graph shows a much smaller detection pattern 

with walks that are parallel to the sensor face. This direction results with less of a Doppler 

frequency shift; the Doppler shift requires a sufficient amplitude change and duration time to 

cause an alarm. In practical terms, this means that the microwave transmitter sends out a 

known frequency and if a higher or lower frequency is returned to the receiver, the target is 

moving closer or further away from the sensor. 

Figure 42: Differences in detection patterns occur for walk tests that are performed from a variety of 

orientations and from different directions. 

4.2.5 Installation Criteria 

Microwave sensors should ideally be mounted near the ceiling or directly on the ceiling. A rigid 

and stable mounting assembly should be used. The actual location of the sensor (ceiling, 

corner, wall, etc.) will depend on the particular sensor being used, as well as the area or target it 

is intended to protect. 

Care should be taken when surveying the area to be protected to note any object that may 

degrade the detection capability of the sensor (metal filing cabinets, fans, air conditioner vents, 

etc.). Because microwave energy is difficult to constrain, special care should also be taken 

when locating and directing the energy within the area requiring detection. A protected volume 

surrounded by masonry or metal construction confines microwave energy and prevents 

detection outside the protected volume, thus preventing one common source of nuisance 

alarms. 
 4-12 

Fluorescent lights located in the sensor detection envelope, especially at distances of less than 

3 meters (about 10 feet), may cause low-frequency Doppler shifts, originating with reflections 

from the ionized gas within the fluorescent tubes. Blocking the line-of-sight path, by using either 

a metal mesh of 0.6 centimeters (0.25 inches) mesh or a radiofrequency absorber, eliminates 

such signal interference.

4.2.6 Sensor Testing 

A regular program of testing sensors is imperative for maintaining them in optimal operating 

order. Three types of testing need to be performed at different times in the life of a sensor: 

acceptance testing, performance testing, and operability testing. 

4.2.6.1 Acceptance Testing 

When a sensor is first installed, it should be tested in order to formally “accept” the sensor as 

part of the facility’s physical protection system. Acceptance testing consists of two parts: 

(1) A physical inspection to ensure that the sensor is installed properly consists of the 

following: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify that signal and power wires are routed in the conduit. 

 Verify proper power levels (voltage and amperage). 

 Verify correct wire connections. 

(2) A performance test to establish and document the level of performance. Refer to the 

following section for details.

4.2.6.2 Performance Testing 

Performance tests (refer to Figure 42) are designed to verify the level of performance of each 

microwave sensor through the range of intended function. This testing will verify the 

manufacturer’s published detection pattern or will establish the actual detection pattern. 

This test should include a visual inspection of the sensor and of the general area where the 

sensor is installed. Prudent routine maintenance should be performed according to the 

maintenance section. 

All relevant processor readings should be recorded, and new readings should be compared to 

the last recorded readings. As in all test situations, the area under test should be maintained 

under visual observation by a member of the site security force, or a member of the site security 

force should actually conduct the test. For each sensor, the test should, where possible, do the 

following: 

 Ensure that the system meets the manufacturer’s specifications and recommended 

detection probability. 

 Verify that no disabling dead spots exist in the zone of protection. 
 4-13 

 Verify that line supervision and tamper-indication alarms in both the access and secure 

modes are functional. 

 Verify that both line supervision and tamper-indication alarms are received in the alarm 

station as appropriate. 

Records of initial testing capabilities, equipment sensitivity setting, or voltage outputs should be 

maintained so that deterioration in equipment capability can be monitored. Walk tests should be 

performed for all areas covered by the microwave sensor, and compared with the results of the 

acceptance test to check for any degradation in the coverage of the sensor. 

4.2.6.2.1 Radial Path Testing

The following instructions describe the walk test to be conducted along the radial (parallel to the 

common center of the detection zone) paths (refer to Figure 43), which is the most effective 

detection approach against a microwave. 

(1) Start outside of the published detection area in front of the sensor, and walk at 1 foot per 

second along the first radial path. 

(2) Stop when an alarm occurs and mark that position. 

(3) Return to the start point, wait 30 seconds for the sensor to reset, and repeat the walk 

test along the same path. 

(4) Repeat testing on that path until the required number of tests is completed. Multiple 

tests along each test line path are required to establish a PD (probability of detection). 

As an example, to establish that a sensor has a minimum PD of 90 percent at a 

confidence level of 95 percent, the sensor would have to pass 29 out of 30 tests. 

(5) Perform Steps 1 through 4 for the remaining radial paths. 

4.2.6.2.2 Tangential Path Testing

The following instructions describe the walk test to be conducted along the tangential (lateral or 

perpendicular to the common center of the detection zone) paths (refer to Figure 43), which are 

the least effective detection approach against a microwave. 

(1) Start outside of the published detection area on one side, and walk at 1 foot per second 

along the first tangential path. 

(2) Stop when an alarm occurs and mark that position. 

(3) Return to the starting point, wait 30 seconds for the sensor to reset, and repeat the walk 

test along the same path. 

(4) Repeat testing on that path until the required number of tests is completed. Multiple 

tests along each test line path are required to establish a PD (probability of detection). 

As an example, to establish that a sensor has a minimum PD of 90 percent at a 

confidence level of 95 percent, the sensor would have to pass 29 out of 30 tests. 

(5) Perform the above tests on remaining paths. 
 4-14 

(6) Repeat Steps 1 through 5, starting from the other side of the detection area. 

Figure 43: Recommended walk test paths and directions for the performance testing of a microwave 

sensor. 

4.2.6.2.3 Slow Walk Tests

Slow walk tests are conducted at speeds less than 0.5 feet per second. Most volumetric 

sensors such as the microwave will have a speed where detection capability decreases. If the 

potential to circumvent a system by crawling is a concern, crawl testing should be performed to 

obtain detection characteristics. Detection of a crawling person will likely be different than 

detection of a walking person. 

If an equal number of tests for each approach is not possible, the penetration approach pattern 

that is most difficult to detect for a particular sensor should be attempted more frequently. The 

various paths should be tested in random order, which will reduce the possibility that 

environmental effects and other unknown factors are affecting the test results (i.e., detection or 

nondetection). Using a random sequence, there is less chance that the test results would be 

biased. 

4.2.6.3 Operability Testing 

Operability tests for these systems consist of simple walk tests. The testing individual walks 

through the expected detection zone of a sensor and confirms that the alarm has been received 
 4-15 

at the alarm display center. The testing individual should look for any evidence of damage to 

the sensor or tampering with the device. 

4.2.7 Maintenance 

A visual inspection of the installation should be performed quarterly and immediately after major 

maintenance to the building in the sensor area. Mounting brackets and hardware should be 

inspected for stability and corrosion. Frequent visual inspections ensure that no blocking 

objects have been moved into a position that would render the sensor inoperative. Periodic 

tests, in addition to the self-test invoked by the sensor or the system, ensure that the sensor is 

operating effectively. Standby batteries should be replaced on a conservative schedule. Every 

service call should be entered in a log to record the date, time, corrective action, and an 

assessment of the cause of the problem. 

4.3 Passive Infrared

4.3.1 Principles of Operation 

PIR sensors are the most commonly used volumetric sensor for interior applications. Many 

facilities use PIRs for the protection of the interior of rooms or particular areas of a room. (Refer 

to Figure 44.) 

Figure 44: Detection pattern for a typical installation of a PIR sensor. 

PIR sensors detect the electromagnetic radiated energy generated by sources that produce 

temperatures below that of visible light. PIR sensors do not emit any energy field into the area 
 4-16 

they are protecting and do not measure the amount of infrared energy. Rather, PIRs measure 

changes in thermal radiation. PIR sensors detect thermal radiation by sensing the change in 

contrast between a heat source and the ambient background temperature. They are considered 

to be a type of visible sensor because they are in plain view within the area; they also require a 

line of sight between the sensor and any target to be detected. The sensor detects intrusions 

as a function of the magnitude of the difference between the intruder’s temperature and the 

background temperature. 

Using parabolic mirrors or Fresnel lens optics, the infrared energy is focused on the detector 

chip in the sensor. Using either variety of lens, the detection pattern is subdivided into solid 

angular segments. (Refer to Figure 45.) As a person passes across the detection segments, 

each segment passed through will generate an increase or decrease in temperature, which will 

trigger an alarm. This infrared energy is detected by a thermopile or pyroelectric device and 

converted into an electrical signal. This signal is then processed by circuitry in the sensor which 

determines whether this constitutes an alarm. The electronic processing can be a count of the 

number of signal pulses over the detection threshold and will generate an alarm only when a 

specified number of pulses occurs within a certain time period. An alarm is annunciated when 

the difference between an intruder and the ambient background temperature reaches a 

predetermined value. On some sensors, this difference can be as small as 1 degree Celsius. 

Figure 45: A PIR sensor’s detection pattern is subdivided into solid angular segments; a specific number of 

segments must detect an anomaly before the sensor will signal an alarm condition. 

While infrared radiation is invisible to the human eye, infrared radiation emitted by an object is 

directly related to its temperature. The infrared region lies between 0.75 and 

1,000 micrometers. The human body radiates infrared energy in the 8 to 14 micrometer region.

PIR sensors continuously receive infrared energy from all objects within an area being 

protected. Ceilings, walls, floors, furniture, and other objects all emit infrared energy 

proportionate to their temperature and emissivity (emissivity defines how well an object absorbs 

and radiates infrared energy). A PIR will respond only to changes in the received infrared 
 4-17 

energy. The absorption and radiation of infrared energy depend on the composition of the 

surface of the object. 

4.3.2 Types of Passive Infrared Sensors 

By configuring the parabolic mirrors or Fresnel lens, a single conical field (referred to as a 

“curtain PIR”), a multiple segment field, or a hemispherical field of view can be generated, as 

shown in Figure 46 and Figure 47. 

Figure 46: An example of a curtain PIR application. 

Figure 47: These two diagrams illustrate the detection pattern of a ceiling-mounted PIR sensor (top view and 

side view). This configuration is also known as the hemispherical pattern. 

7 to 20 foot 

max height 

20 to 45 foot 

max distance 3 to 4.5 foot 

max width 
 4-18 

4.3.3 Sources of Nuisance Alarms in Passive Infrared Sensors 

Any object causing an appropriate temperature differential can potentially generate a nuisance 

alarm in a PIR sensor. The required temperature differential can be caused by rapid changes in 

localized heating and cooling, which may be affected by the following: 

 Sunlight 

 Incandescent light bulbs 

 Radiators 

 Space heaters 

 HVAC vents 

 Hot pipes 

In practice, nuisance alarms are less likely to be generated by localized heating and cooling 

because temperature changes generally do not happen rapidly. All hot spots that generate 

infrared energy should be removed or shielded. Radiant energy from such sources may 

produce thermal gradients that change the background energy pattern. Hot spots can be open 

heating elements, incandescent light bulbs, convective heat currents, and direct sunlight on 

windows, floors, and walls. 

Sunlight can enter the protected area directly through openings, such as broken window panes, 

ventilation grids, and poorly fitted doors. Small animals or large insects moving in the PIR 

sensor field of view may also be detected. Devices that retain the required temperature 

differential and sway into the sensor field of view may generate nuisance alarms. 

The vibration of a PIR sensor may trigger an alarm by causing a heat source to appear as if it 

were moving. Insects crawling on elements inside the sensor or condensation forming within 

the sensor may also cause nuisance alarms. 

The detector elements in a PIR sensor can be subject to interference from various 

electromagnetic fields generated by electromagnetic devices, such as hand-held radios. 

However, infrared sensors are not generally subject to nuisance alarms caused by sound, 

electrical disturbances, or radio disturbances. 

4.3.4 Characteristics and Applications 

PIRs are installed so that the detection pattern covers the area or asset to be protected. This 

detection pattern can be pictured as a “searchlight beam” that gradually widens as the zone 

extends farther from the sensor with some segments being illuminated while others are not. 

This design characteristic allows the user to focus the beam on areas where detection is 

needed while ignoring other areas, such as known sources of false alarms. 

Changes in the infrared signature of an object (including people) are most visible when the 

object moves laterally through the detector’s range. Positioning a detector so that an intruder 

must walk across the detector’s range is much more effective than positioning the detector so 

that an intruder would likely walk toward the detector. 
 4-19 

The presence and/or location of a passive sensor is more difficult for an intruder to determine 

than an active sensor, putting the intruder at a disadvantage. 

In environments where explosive vapors or explosive materials may be present, passive 

sensors are safer than active ones because no potentially explosion-initiating energy is emitted. 

Multiple passive sensors can be placed in a volume without interfering with each other 

(interacting) because no signals are emitted. 

Detection effectiveness is less than optimal for motion directly toward or away from the sensor. 

Since the PIR is a line-of-sight detector, the field of view can be easily blocked by cubicle 

partitions or furniture. 

Sources of rapid temperature changes can cause nuisance alarms. Sensitivity changes with the 

temperature of the detection area. If the ambient temperature is near the body temperature of 

an intruder, the intruder could possibly enter undetected. 

Slow-moving targets can be a problem. A PIR sensor will not detect very slow motion. 

However, defeating a PIR sensor with slow motion is difficult to do because a person must keep 

all body movement to a minimum. 

A PIR sensor may fail to detect movement in an area if the lens is masked or fogged. 

4.3.5 Installation Criteria 

Installation of PIR sensors is fairly inexpensive. The manufacturer’s guidelines should be 

followed as appropriate. 

All hot spots that generate infrared energy should be removed or shielded. Radiant energy from 

such sources may produce thermal gradients that will change the background energy pattern. 

Hot spots can be open heating elements, incandescent light bulbs, convective heat currents, 

and direct sunlight on windows, floors, and walls. Sunlight can enter the protected area directly 

through openings, such as broken window panes, ventilation grids, and poorly fitting doors. 

For optimal intruder detection, the sensor should be aimed so that the path likely taken will be 

across the sensor field of view, rather than toward or away from the sensor. 

To prevent an intruder from circumventing the sensor, its detection envelope should not be 

smaller than the physical boundaries of the area being protected. The detector should not be 

mounted directly above a doorway or a window or in any position that would allow an intruder 

access to the sensor from beneath the sensor. 

For high-security applications, the small LED light on the sensor that indicates a detection 

should be turned off when not being tested by authorized personnel. 

Placing the sensor near a light source can generate nuisance alarms caused by insects 

attracted to the light. 
 4-20 

All sensors should be provided with the following: 

 Supervised wiring in conduit 

 Fail-safe operation 

 Emergency power in case of main power failure 

 Tamper indication 

An end-to-end self-test is desirable. A final test should be performed after installation to verify 

the sensor coverage area. 

4.3.6 Testing 

A regular program of testing sensors is imperative for maintaining them in optimal operating 

order. Three types of testing need to be performed at different times in the life of a sensor: 

acceptance testing, performance testing, and operability testing. 

4.3.6.1 Acceptance Testing 

When a PIR sensor is first installed, it should be tested in order to formally “accept” the sensor 

as part of the physical protection system. Acceptance testing consists of two parts: 

(1) A physical inspection to ensure that the sensor was installed properly consists of the 

following: 

 Verify that the installation matches the installation drawings, which should follow 

the guidance provided by the manufacturer. 

 Verify that signal and power wires are routed in the conduit. 

 Verify proper power levels (voltage and amperage). 

 Verify correct wire connections. 

(2) A performance test to establish and document the level of performance consists of 

following the performance testing procedure (described below for the recommended 

tests. 

4.3.6.2 Performance Testing 

Performance tests are intended to verify that the level of performance of each PIR sensor is 

consistent with the documented performance achieved during the original acceptance testing. 

Performance testing should be conducted whenever an electronics module is replaced, the 

optical alignment is changed, or an adjustment is made that can affect sensitivity. This test 

should include a visual inspection of the sensor and of the general area where the sensor is 

installed. Personnel conducting the test should refer to the maintenance section and perform 

the prudent routine maintenance. Test procedures recommended by the manufacturer should 

be followed. As in all test situations, the area being tested should either be kept under visual 

observation by a member of the site security force, or a member of the site security force should 

conduct the test. 
 4-21 

For each area of detection, the test should do the following: 

 Ensure that the system meets the manufacturer’s specifications and recommended 

detection probability. 

 Verify that no dead spots exist in the zone of protection. 

 Verify that line supervision and tamper-indication alarms in both the access and secure 

modes are functional. 

 Verify that both line supervision and tamper-indication alarms are received in the alarm 

station as appropriate. 

Records of initial testing capabilities, equipment sensitivity settings, or voltage outputs should be 

maintained so that deterioration in equipment capability can be identified and monitored. 

Walk tests should be performed for all areas covered by the PIR sensor and compared with the 

results of the initial acceptance test to check for any degradation in the coverage of the sensor. 

4.3.6.2.1 Tangential (Arc) Path Testing

The following instructions describe the walk test to be conducted along tangential paths (refer to 

Figure 48); this approach has the likeliest chance of detection as the PIR sensor is most 

sensitive in this direction. 

(1) Start outside of the published detection area on one side and walk at 1 foot per second 

along the first tangential path. 

(2) Stop when an alarm occurs and mark that position. 

(3) Return to the starting point, wait 30 seconds for the sensor to reset, and repeat walk test 

along the same path. 

(4) Repeat testing on that path until the required number of tests is completed. Multiple 

tests along each test line path are required to establish a PD (probability of detection). 

For example, in order to establish that a sensor has a minimum PD of 90 percent at a 

confidence level of 95 percent, the sensor would have to pass 29 out of 30 tests. 

(5) Perform the steps above on remaining paths. 

(6) Repeat Steps 1 through 5, starting from the other side of the detection area. 
 4-22 

Figure 48: Recommended walk test paths and directions for the performance testing of a PIR sensor. 

4.3.6.2.2 Radial Path Testing

The following instructions describe the walk test to be conducted along the radial paths (refer to 

Figure 49); this approach has the least likely chance of detection as the PIR sensor is least 

sensitive in this direction. 

(1) Start outside of the published detection area in front of the sensor and walk at 1 foot per 

second along the first radial path. 

(2) Stop when an alarm occurs and mark that position. 

(3) Return to the start point, wait 30 seconds for the sensor to reset, and repeat walk test 

along the same path. 

(4) Repeat testing on that path until the required number of tests is completed. Multiple 

tests along each test line path are required to establish a PD (probability of detection). 

For example, in order to establish that a sensor has a minimum PD of 90 percent at a 

confidence level of 95 percent, the sensor would have to pass 29 out of 30 tests. 

(5) Perform Steps 1 through 4 for the remaining radial paths. 
 4-23 

Changes in room configuration can affect sensor coverage and should be checked. If room 

configuration has changed significantly, a complete retest of the sensor coverage should be 

initiated to ensure the protection of the room or the asset. 

The test should determine the most vulnerable area for each section and the method of 

approach most likely to penetrate (e.g., walking, running, jumping, crawling, rolling, or climbing). 

This determination will, in most cases, be sensor and location dependent. The penetration 

approach that is most difficult to detect should be attempted more frequently if an equal number 

of tests for each approach is not possible. 

The various approach paths should be tested in random order, which will preclude the possibility 

that environmental effects and other unknown factors are affecting the test results (detection or 

nondetection). Use of a random sequence reduces the chance that the test results will be 

biased. 

When a designer is determining the best place to locate an asset within a room, the enclosed 

sample graph showing the PIR sensor detection pattern could be used as guidance (refer to 

Figure 49). The asset should be placed inside the area that has a high PD, no matter the 

direction from which the intruder approaches the sensor. 

Figure 49: A typical PIR detection pattern derived from walk tests towards the sensor. 
 4-24 

4.3.6.3 Operability Testing 

Operability testing should be conducted by crossing the zone of detection in the area that the 

sensor is installed to monitor. The detection capabilities of each PIR should be walk tested in a 

different, preferably random, order every 7 days, and the tests should be conducted throughout 

the week rather than all on the same day. The testing should result in 100-percent detection on 

all segments every 7 days. If the interior intrusion alarm system fails to detect an intrusion in 

one or more segments, corrective actions should be taken and documented. Records should 

be maintained to document that all required testing has been accomplished. 

4.3.7 Maintenance 

The general maintenance guidelines outlined in the manufacturer’s technical manuals should be 

followed on a schedule determined by security maintenance staff and security forces, as well as 

by the environment in which the sensor is installed. 

At a minimum, the sensor optics should be periodically cleaned and frequent visual inspections 

performed to ensure that no objects have been moved into a blocking position that would render 

the sensor inoperative. 

Equipment maintenance guidelines generally recommend keeping 10 to 20 percent of spare 

parts on hand, based on total facility units. This requirement may be adjusted as maintenance 

data are accumulated on the failure rate of specific sensors and sensor components. If 

replacement parts can be obtained quickly from regional distributors, smaller onsite inventories 

would be adequate. 

4.4 Proximity Sensors

4.4.1 Principles of Operation 

Proximity sensors, also known as point protection/detection devices, have the capability of 

detecting someone approaching, touching, or attempting to remove valuable items. Proximity 

sensors usually form the innermost level of protection, after exterior perimeter sensors, 

boundary penetration sensors, and/or volumetric sensors. Since they are usually located close 

to a particular asset, the response force has the least amount of time to respond to an alarm 

once the intruder is detected. Because of this, proximity sensors should not be used as primary 

detection on a high-risk item. Proximity sensors are most effective for protection against an 

insider. 

4.4.2 Types of Proximity Sensors 

Types of proximity sensors include the following: 

 Capacitance 

 Pressure 

 Strain 

 Switches 
 4-25 

The various types of proximity sensors are described below. 

4.4.2.1 Capacitance 

Capacitance proximity sensors operate on the same principle as an electrical capacitor. These 

types of detectors are used to protect metal containers that can be isolated from ground such as 

safes or file cabinets. An electrical capacitor comprises one or more conductors separated by a 

dielectric medium. A change in the electrical characteristics of the dielectric medium causes a 

change in the capacitance between the two plates. In the case of the capacitance proximity 

sensor, the protected metal object corresponds to one plate, and an electrical reference ground 

plane under or around the protected object corresponds to the second plate. An insulator 

isolates the protected object from ground. The air between the object and ground comprises 

the dielectric medium. When a person comes close to, or touches the object, the dielectric is 

changed, which changes the capacitance. The processor (part of the capacitance sensor) 

detects the change in capacitance and generates an alarm. 

4.4.2.2 Pressure 

Pressure sensors incorporate a sensing device that responds to deformation of the sensor 

caused by weight placed on it. Pressure mats consist of a series of ribbon switches positioned 

parallel to each other, approximately 3 inches apart along the length of the mat. Ribbon 

switches are constructed from two strips of metal in the form of a ribbon separated by an 

insulating material. They are constructed so that when an adequate amount of pressure, 

depending on the application, is exerted anywhere along the ribbon, the metal strips make 

electrical contact. They can be used to detect the presence of intruders when they approach or 

attempt to move protected items. For instance, pressure mats can be installed under the carpet 

around the protected item. Then anyone who approaches the item steps on the mat and 

initiates an alarm. The operation of a pressure mat represents the operation of pressure 

sensors in general. The pressure sensor output signal is routed to an alarm console to indicate 

an intrusion.

4.4.2.3 Strain 

Strain sensors measure small amounts of deformation or flexing of a surface. A basic 

configuration of a strain sensor would be one or more sensing devices connected to a 

processor. The sensing devices can employ piezoelectric, piezoresistive, metal foil, or wire to 

detect surface deformation or flexing. When configured to be a strain sensor, the electrical 

properties (such as resistance) of these materials will change when bent, stretched, or 

compressed. The processor continually measures the electrical properties of the sensing 

device and will output an alarm or other indication when a specified amount of change has 

occurred. Processors will typically have user-programmable controls to specify how much 

change has to occur in order to output an alarm. In a proximity sensor application, the sensing 

device is attached to a surface that is flexed slightly when an object (such as a protected item) 

is placed on it. The processor is programmed to alarm if there is a change, such as when the 

object is removed or tampered with. 

4.4.2.4 Switches 

Switches can be used as a proximity point sensor. A protected item is placed on the switch, 

actuating it so that the electrical contacts are either in an open or closed position. Alarm system 
 4-26 

electronics monitors the switch for a change in the position of the contacts. If the item is 

removed, the contacts change position and an alarm is generated. Movement of the item can 

also cause an alarm if the movement is such that it causes the switch contacts to change 

positions. The surface and switch mounting need to be designed so that it is very difficult to 

remove the protected item while maintaining the switch in the secured position. 

4.4.3 Sources of Nuisance Alarms 

The sensitivity of capacitance sensors is affected by changes in relative humidity and the 

relocation of other metal objects closer to or farther away from the protected item. Changes in 

the relative humidity vary the dielectric characteristics. A rapid increase in humidity causes the 

dielectric (air) conductivity to increase and reduces the capacitance, resulting in an alarm. 

Conversely, a decrease in humidity or drying of the air reduces the conductivity. Similarly, when 

larger metal objects (high electrical conductivity) such as cabinets, desks, equipment racks, etc. 

are moved close to an object protected by a capacitive sensor, the sensitivity of the sensor can 

change. If the sensitivity is increased, the chance for nuisance alarms increases. If the 

sensitivity is lowered, detection capability is lowered. 

Nuisance alarms from pressure mat sensors can occur if the insulating or separating material 

that keeps the ribbon switch contacts apart deteriorates because it is worn out or exposed to 

harsh conditions. Extreme heating and cooling (out of the operating range) are additional 

nuisance alarm sources, especially if the mat is worn and deteriorated. A mat installed near 

heavy traffic areas where workers or other personnel would inadvertently step on it is an 

additional source of nuisance alarms. Pressure mats that are in good condition and installed 

properly should have very few nuisance alarms. 

Strain sensor devices can be affected by changes in temperature, which result in nuisance 

alarms. Some strain sensors are configured to reduce or eliminate the effects of temperature 

changes. Changes in humidity can also be a source of nuisance alarms. If the protected item 

can absorb moisture, the weight of that object could change enough with humidity changes to 

cause nuisance alarms. 

Switch sensors in good condition and installed properly should have very few, if any, nuisance 

alarms. Primary nuisance sources include loose or damaged mounting brackets, fasteners, and 

mounts and damaged or worn out internal or external components of the switch itself. 

4.4.4 Characteristics and Applications 

Proximity sensors should not be used as primary detection for high-risk items. They are 

typically used as a second or third line (layer) of protection and are most effective for protection 

against an insider. The goal would be to detect the insider who is very close to, touching, or 

moving an object that he or she should not have access to. Portable high-value objects should 

be in a cage or safe or tied down to add delay to an abrupt theft. (See Figure 50.) Portable, 

high-risk/value items should be locked in cabinets or secured by other means to add delay in 

removal. Proximity sensors can be installed to detect attempted removal of tiedowns or opening 

of cabinets. 
 4-27 

Figure 50: Example of portable, high-value items. 

A typical application of a capacitance proximity detector would be the protection of a safe or file 

cabinets (see Figure 51). The safe or file cabinets must be set on blocks to isolate them from 

the ground plane. The blocks should be made of a nonconductive plastic or nonhydroscopic 

material. Wooden blocks should not be used because they are hydroscopic and could absorb 

enough moisture over a period of time to change the dielectric enough that the protected objects 

become insensitive. Capacitive detectors can be used to protect paintings, tapestries, and other 

objects by installing a relatively large copper foil sheet or metal screen under the objects 

requiring protection. In this type of application, the metal screen becomes part of the protected 

circuit, as is the safe or any other metal object. 

Pressure mats are commonly used in industrial and commercial applications such as controls 

for opening doors or as safety devices for machinery. Although less common in security 

applications, they can be used along probable intruder routes or around valuable objects. They 

are usually well concealed under carpets or flooring to make it more difficult for an intruder to 

determine the location of the detection area. 
 4-28 

Figure 51: Example of a capacitance sensor installation. 

Strain sensors can be used to continually monitor the weight of an object, sensing when it is 

being lifted, moved, or tampered with (Figure 52). The environment, such as changes in 

temperature or humidity, must be considered. Strain sensors can also be used to detect a 

person’s weight as he or she approaches a protected area or item (Figure 53). 

A self-adjusting capacitance proximity sensor may be defeated by extremely slow approach to 

the protected object. An adversary can detect the presence of a capacitance proximity sensor 

by employing radiofrequency field-sensing equipment, such as that used by a telephone 

company to find underground telephone cables. Relocating any conducting object closer to or 

farther away from the protected surface can cause a small capacitance change between the 

protected surface and ground, generating a nuisance alarm. These objects include persons 

walking near or leaning on the surface, cabinets or other objects being moved close to the 

surface, or loose-fitting components of the protected object itself. 

Figure 52: Pressure mat example. 
 4-29 

Figure 53: Strain sensor concept to detect person on stairs. 

A capacitance sensor may not work well (i.e., high nuisance alarms) if the protected object is in 

an area where there is high traffic close to the object when the sensor is in the secured 

condition. 

The sensitivity of a capacitance proximity sensor is affected by sudden changes in the relative 

humidity. Changes in the moisture content of the air will vary the dielectric characteristics by 

either increasing or decreasing its conductivity. If the sensor sensitivity is adjusted to detect an 

intruder several meters from the object, the change in conductivity may be enough to initiate a 

nuisance alarm. Capacitance proximity sensors employing a self-balancing circuit adjust 

automatically to changes in relative humidity and to relocation of conducting objects near the 

protected object. 

A pressure sensor is vulnerable to bridging by a board placed on bricks or by jumping or 

stepping across it. A pressure sensor also is subject to considerable wear from normal traffic, 

and periodic tests should be performed to ensure that the sensor is operating effectively. The 

example mat sensor shown in Figure 54 could be used to let room occupants know that 

someone is at the door, but it can be easily bridged if installed this way for security applications. 

A strain sensor responds to any action that causes the surface upon which it is mounted to flex. 

Heavy machinery in the building or nearby heavy vehicular traffic can cause surfaces to vibrate, 

which may result in nuisance alarms. Although the sensor operates at frequencies as low as 

direct current, limiting the low-frequency response avoids alarms caused by long-term drift and 

slow deformation of the structure over time. 

To Strain Sensor Processor 

Strain Sensing Devices 
 4-30 

Figure 54: Mat sensor near door can be bridged if it is not installed correctly. 

4.4.5 General Installation Criteria 

For installation and setup of proximity sensors, manufacturer instructions and recommendations 

should be followed. The sensors should be equipped with a tamper-indicating device that is 

continuously monitored by the security system. These tamper-indicating devices are typically 

switches that detect a cover or door (that allows access to the sensor electronics) being 

removed or opened. All wiring for these systems (alarm, power, or tamper) should be in 

conduit, and the alarm and tamper signal wiring should be supervised. Backup batteries or 

standby power is recommended. Once installed, performance testing is necessary to confirm 

desired detection capability. Testing should include attempting to defeat the sensor using 

defeat methods for the sensor technology. Short-term trial operation (several days to several 

weeks) will help determine if there are any initial and common nuisance alarm sources. An 

end-to-end self test is also desirable. General installation criteria for each type of proximity 

sensor follow. 

4.4.5.1 Capacitance Sensor 

The capacitive sensor will need a ground plane, which could consist of cables, conductive mats, 

or conductive foil under, near, or around the protected object. The protected object will need to 

be isolated from the ground plane using nonhydroscopic materials. Both the protected object(s) 

and the ground plane will need to be connected to the processor unit, which is typically mounted 

on a wall close to the protected object. 
 4-31 

4.4.5.2 Pressure Sensor 

The pressure sensor is usually concealed from an intruder as a doormat or by placing it under 

the floor covering. The sensor pad can be installed in a depression in the floor. If the pad is 

placed under a protective cover, such as a rug or a rubber doormat, the protective cover must 

be fastened down around the edges to prevent the pad from moving or being removed. 

4.4.5.3 Strain Sensor 

Generally the sensing device is mounted at the point where the largest deflection is most likely 

to occur. If that point cannot be defined, the best procedure is to mount the sensor in the center 

of the surface. The sensor is bonded to the surface as rigidly as possible, so when the surface 

flexes, the sensor will be forced to elongate or contract and will not separate or slide along the 

surface. Site- or object-specific design and fabrication of the mounting or attaching surface may 

be required. 

4.4.5.4 Switch Sensor 

This sensor may also require site- or object-specific design and fabrication. Basic installation 

criteria include a way to secure the object to the placement surface, protection of the switch and 

switch wiring from tampering, protection to make it very difficult to remove or move the object 

while maintaining the switch in the secured position, and connection of the switch contacts to an 

alarm communication system. 

4.4.6 Sensor Testing 

4.4.6.1 Acceptance Testing 

When a sensor is first installed, it should be tested in order to formally “accept” the sensor as 

part of the physical protection system. Acceptance testing consists of two parts: 

(1) A physical inspection to ensure that the sensor is installed properly consists of the 

following: 

 Verify that the installation matches the site installation documentation/ drawings, 

which should follow the guidance provided by the manufacturer. 

 Verify that signal and power wires are routed in the conduit. 

 Verify proper power levels (voltage and amperage). 

 Verify correct wire connections. 

(2) Performance testing to establish and document the level of performance is described 

below. 

4.4.6.2 Performance Testing 

Performance testing should include a visual inspection of the sensor and of the general area 

where the sensor is installed. When performing testing, alignment, or adjustments on sensors, 

the assistance of additional personnel should be considered as these activities can be difficult 

for a single person to manage. 
 4-32 

For proximity sensors, performance testing should include tests to verify good detection when a 

protected item and any associated delay hardware is approached, touched, or moved. Specific 

tests will depend on the sensor type and installation configuration. Tests should be conducted 

at different locations around, near, and at the protected object. Several tests at each location 

should be conducted to achieve a confidence level for detection. Performance testing 

procedures should include testing of tamper switches, backup batteries, or power supplies and 

receipt of correct detection and tamper alarms at the alarm stations. 

Sensor-specific performance test procedures should be developed and documented. 

Procedures should include step-by-step test methods, pages or forms to record test results 

(including a sketch of the sensor detection coverage if applicable), a form to record the sensor 

model, serial number, settings, and other data as needed. Test results and data can be 

compared to previous test results to determine trends or the occurrence of gradual degradation. 

Test results and documentation should be protected from unauthorized disclosure. 

4.4.6.3 Operability Testing 

Operability tests should be conducted on proximity devices in a manner in which the sensor is 

designed and installed to function (e.g., activating sensor alarms by opening doors, moving 

through sensored areas, or being close to or touching an object such as a safe). Certain 

proximity sensors require a protected item to be moved or a protective cage or cabinet to be 

opened to activate the alarm (e.g., switch and strain sensors). Testing of these types of alarms 

may require increased coordination with facility personnel to ensure that safety and security are 

maintained during the testing. 

During operability testing, the protected area or asset can be visually inspected to ensure that 

objects have not been placed in the area or near the protected asset that affect the detection 

capabilities of the sensor or could cause nuisance alarms. 

4.4.7 Maintenance 

Periodic operability and performance tests, in addition to any self-test invoked by the sensor or 

the system, need to be performed to ensure that the sensor is operating effectively. A visual 

inspection of the installation should be performed periodically, particularly after any major 

maintenance to the protected surfaces. Standby batteries should be tested on a conservative 

schedule and replaced when indicated. Every maintenance or repair action should be entered 

in a log to record the date, time, corrective action, who performed the maintenance or repair, 

and an assessment of what may have caused the problem. Maintenance activities for each 

sensor are described below. 

4.4.7.1 Capacitance Sensor 

Extremely good housekeeping is required in the area near the protected object because a 

capacitance proximity sensor is very sensitive to the environment within a few inches of the 

protected surface. Any conducting object large enough to change the dielectric of the air that is 

placed near the protected item must be removed. Wet mopping or liquids spilled on wooden 

floors under and around the protected object can significantly change the operation of a 

capacitance sensor. 
 4-33 

4.4.7.2 Pressure Sensor 

A mat-type sensor can be subject to considerable wear from traffic during normal business 

hours, so frequent operability tests are important. During testing, the sensor should be 

inspected for visible signs of wear and degradation. 

4.4.7.3 Strain Sensors and Switch Sensors 

During periodic testing, these sensors should be inspected for loose attaching hardware, loose 

connections and excessively worn parts. 

4.5 Dual-Technology Sensors

4.5.1 Principles of Operation 

Dual-technology sensors (also referred to as “dual techs”) were designed to lower the false or 

nuisance alarm rates in an interior sensor. This is accomplished by combining two different 

types of sensors in one casing so that each sensor is complementary: each sensor generates a 

different set of nuisance alarm sources. The two sensors are connected electronically by using 

an “AND” gate logic function; both technologies need to sense an event within a predetermined 

interval before a valid alarm will be generated. If one technology has a detection but the other 

does not, no alarm will be generated. Because the two sensors will not sense an intrusion at 

the same instant, the system is designed to generate an alarm when both sensors sense an 

intrusion in a preselected time interval, usually a few seconds. This time interval is usually a 

parameter that the user can configure. 

Reducing the nuisance alarm rate of a sensor is highly desirable. However, this feature comes 

at a price: making a unit less sensitive to possible nuisance alarms also makes the unit less 

sensitive to valid alarm conditions. Because of this possibility, dual-technology sensors 

configured to operate in an “AND” gate logic are not normally recommended for high-risk or 

high-security facilities. 

Less commonly, dual-technology sensors can be designed to operate using “OR” gate logic. 

With the OR configuration, either sensor technology can generate an alarm independent of the 

other. This configuration is similar to having two separate sensors installed in the same 

location. Unfortunately, two different types of sensors are not likely to both be optimally 

installed in the same location. For example, a PIR sensor would be best placed such that an 

adversary would likely walk across the detection zone, while a microwave sensor would be best 

positioned such that an adversary would likely walk toward or away from the detection unit. 

Therefore, in high-risk facilities, the installation of two different types of sensors in locations that 

are optimal to their own detection capabilities would be preferable to the use of a 

dual-technology sensor configured with an “OR” gate logic. (See Figure 55.) 
 4-34 

Figure 55: The figure on the left depicts an overhead view, and the figure on the right depicts a side view, of 

the patterns of detection for a dual-technology sensor comprising a PIR sensor and a microwave sensor; the 

pale yellow “bubble” illustrates the microwave detection pattern, and the remaining “fingers” illustrate the 

PIR detection pattern. Note that most dual-technology sensors use “AND” logic for the two different 

sensors, such that both sensors would have to sense a detection before the sensor would signal an actual 

alarm. 

4.5.2 Types of Dual-Technology Sensors 

Two combinations of dual-tech sensors are usually used for interior protection: Passive Infrared 

Acoustic and Passive Infrared Microwave. Numerous manufacturers build these sensors with 

varying technical specifications so care should be taken in selecting the sensor that meets the 

needs of the particular application. 

4.5.2.1 Passive Infrared Acoustic 

The PIR-acoustic dual-technology unit employs a PIR sensor and usually an ultrasonic sensor. 

The ultrasonic sensor generates a teardrop-shaped pattern of acoustical energy at frequencies 

well above those audible to humans. The patterns are typically about 9 meters (30 feet) deep 

and 7.6 meters (25 feet) wide. They detect disturbances in the reflected energy from anyone 

moving in a radial direction in the energy pattern. The shape of the PIR detection segments is 

similar to the ultrasonic energy pattern configuration. Someone moving in the zone of detection 

will create an alarm if detected by both the PIR sensor and ultrasonic sensor. 

4.5.2.2 Passive Infrared Microwave 

The PIR-microwave dual-technology unit employs a PIR sensor and a microwave sensor. The 

microwave sensor detects Doppler changes in the reflected microwave energy pattern produced 

by someone moving in the area with some radial velocity relative to the detector. This teardropshaped pattern typically covers an area about 20 meters (65 feet) deep and 15 meters (50 feet) 

wide. The shape of the PIR detection segments is also similar to the microwave energy pattern 

configuration (Figure 55). 
 4-35 

4.5.3 Sources of Nuisance Alarms 

Because dual-technology sensors are normally configured to operate with “AND” logic, the 

likelihood of nuisance alarms is greatly reduced. If operated with “OR” logic, sources of 

nuisance alarms will be the sum of sources of nuisance alarms for the individual sensors. 

The PIR detector within most dual-technology units can trigger false alarms from sources of 

heat, sunshine, and incandescent lights, as well as other sources. (See “Sources of Nuisance 

Alarms in Passive Infrared Sensors” in Section 4.3 of this report.) 

For the PIR-acoustic dual-tech sensor, the ultrasonic sensor effectiveness is reduced by air 

turbulence from heating or air-conditioning ducts, drafts, or other sources of moving air. 

Acoustic energy generated by ringing bells and hissing noises, such as the noises produced by 

radiators or compressed air systems, contains frequency components in the operating 

frequency band of ultrasonic motion detectors. These sources of ultrasonic energy may 

occasionally produce signals similar to an intruder, which can confuse the signal processor and 

result in nuisance alarms. 

For a PIR-microwave dual-tech sensor, one important characteristic to remember is that 

microwave energy can pass through light construction material, which can be a source of 

nuisance alarms. 

It is also important to remember that for a dual-technology sensor, when two sensors are 

logically combined using an “AND” gate, the probability of detection of the combined detectors 

will be less than the probability of detection of the individual detectors. The probability of 

detection of the combined sensors in a single unit will be less than if the individual detectors are 

mounted perpendicular to each other with overlapping energy patterns and fields of view. 

4.5.4 Characteristics and Applications 

Dual-tech sensors usually have a lower nuisance alarm rate than single technology sensors 

when the detectors are properly applied and assuming that each has a low nuisance alarm rate. 

This sensor type attempts to achieve absolute alarm confirmation (i.e., no nuisance alarms) 

while maintaining the highest probability of detection (PD) possible for this kind of unit. 

The main advantage of a PIR-microwave dual-tech sensor is that both the PIR and the 

microwave are complementary in providing long, narrow fields of detection. The false alarm 

rate is reduced significantly by the combination of the technologies in the AND configuration. 

These types of sensors would best be used as a proximity-type sensor where detection is 

confined to a small area or a single object. 

A PIR-acoustic dual-tech sensor can typically cover open areas approximately 7.6 meters (25 

feet) by 7.6 meters (25 feet). A feature of ultrasonic energy is that it will not penetrate physical 

barriers such as walls; therefore, it can be easily contained in closed rooms. Since acoustical 

energy will not penetrate physical barriers, the walls of the protected room either absorb or 

reflect the energy. 

Ceiling-mounted transceivers generate a cone-shaped energy pattern that can cover a circular 

area about 9.1 meters (30 feet) in diameter when the transceiver is mounted 3 to 4.6 meters (10 

to 15 feet) above the floor. A ceiling-mounted transceiver can be mounted directly over the area 

requiring protection. This feature is especially valuable in areas where it is difficult to protect 
 4-36 

using wall-mounted transceivers. Long-range ultrasonic transceivers are available with long, 

narrow energy patterns for protecting aisles and hallways. A single detector of this type can 

protect a hallway about 21.3 meters (70 feet) long. Combined microwave and infrared detectors 

cover open areas from 12.2 meters (40 feet) deep and 7.6 meters (25 feet) wide up to 22.9 

meters (75 feet) deep and 13.7 meters (45 feet) wide as well as long, narrow areas up to 61 

meters (200 feet) long. 

When sensors are combined in a logical “AND” configuration, the PD of the combined detectors 

is less than the PD of the individual detectors. If an ultrasonic sensor with a 0.95 PD is combined 

with a PIR sensor having a 0.95 PD, then the resulting 0.90 PD for the dual–tech sensor is the 

product of the individual probabilities. A PD of 0.90 may not meet the required probability of 

detection for some facilities. 

Assuming a single direction of intrusion, a higher PD can be obtained from separately mounted 

sensors than from a dual-technology sensor. Ultrasonic and microwave sensors have their 

highest PD for radial motion either toward or away from the sensor, but a PIR sensor has its 

highest PD for motion circumferentially across its field of view. Thus, the PD for the sensors 

combined in a single unit and aimed in the same direction is less than the PD for individual 

detectors mounted perpendicular to each other with overlapping detection envelopes. The 

highest PD for a dual-tech sensor is achieved by treating the individual sensors separately, in an 

“OR” configuration. 

Vulnerabilities for a dual-technology sensor include vulnerabilities for each sensor technology. 

In the “AND” configuration, if either sensor is defeated, then the dual-technology sensor unit is 

defeated. For this reason, a dual-technology sensor should never be used as a replacement for 

two separately installed sensors in high-security applications. If a dual-technology sensor is 

necessary in a location because of nuisance alarm issues, then another sensor (dual- or singletechnology) should be used and installed in such a manner that each sensor unit protects the 

other, as well as providing overlapping detection coverage within the area being protected. 

It is important to avoid environments where either detector type would be prone to false alarms. 

If either detector is exposed to an environment where it experiences a high number of false 

alarms, then the probability of one of these false alarms being present at the logic AND gate 

when a false alarm arrives from the second, and perhaps more stable, sensor is high. For 

example, if a PIR-acoustic detector was installed in a drafty area where the ultrasonic detector 

would experience a high number of false alarms because of the distortions in its projected 

energy pattern and the infrared detector might experience a few alarms as the result of 

background temperature changes caused by the drafts, the probability of simultaneous alarms 

from both sensors would be increased. A combination microwave and infrared detector would 

be a better choice for such an application because the microwave detector would not be 

affected by this environment. The drafts would still cause temperature changes that could affect 

the infrared detector, but since it would be combined with the microwave detector, the 

probability of simultaneous false alarms would be low and, consequently, the false alarm rate 

would be lower. 

One concern when using a dual-tech sensor that combines microwave and infrared detectors 

with “AND” logic is that the microwave’s detection zone is usually much larger than the 

infrared’s detection zone; hence, no detection will occur until the adversary reaches the point 

where both sensors can detect. 
 4-37 

4.5.5 Installation Criteria 

Microwave technology is usually more sensitive in its least sensitive direction than the PIR in its 

least sensitive direction. Because of this, the following considerations apply: 

 Performance testing and evaluation should be similar to that of a PIR sensor. 

 The sensor should be installed with primary consideration given to the PIR section. The 

most likely paths to the protected item or area should cross through the PIR detection 

pattern and not be directly toward or away from the sensor unit. 

 A dual-technology sensor should be located so that the likely path of an adversary will 

be across the sensor detection area and less likely to be toward the sensor. 

A dual-technology sensor should be installed using a sturdy mount. Vibration can cause 

misalignment or make the sensor prone to nuisance alarms. The installer should make sure 

that the sensor is aligned away from possible nuisance alarm sources such as heaters. 

If dual-technology sensors are to be used, multiple sensor units should be installed, with each 

unit offering overlap protection of the other. 

4.5.6 Testing 

A regular program of testing sensors is imperative for maintaining them in optimal operating 

condition. Three types of testing need to be performed at different times in the life of a sensor: 

acceptance testing, performance testing, and operability testing. 

4.5.6.1 Acceptance Testing 

When a dual-technology sensor is first installed, it should be tested in order to formally “accept” 

the sensor as part of the physical protection system. Acceptance testing consists of two parts: 

(1) A physical inspection to ensure that the sensor is installed properly, consisting of the 

following: 

 Verify that the installation matches the installation drawings (and the drawings 

should follow the installation guidance provided by the manufacturer). 

 Verify sensor intersection spacing. 

 Verify that signal and power wires are routed in conduit. 

 Verify proper power (voltage, amperage) levels. 

 Verify correct wire connections. 

 Perform a complete alignment in accordance with the manufacturer’s manual on all 

units to verify that all modules are operational and oriented correctly. The method 

of physical alignment is specific for each manufacturer’s model. 

(2) Performance testing should establish and document the baseline level of performance 

(see below for a description of the recommended tests). 
 4-38 

4.5.6.2 Performance Testing 

Performance testing and evaluation should be similar to that of a PIR sensor. (See 

Section 4.3.6.2.) The most likely path to the protected item or area should ideally cross through 

the PIR detection pattern and not be directly towards or away from the sensor unit. In addition 

to the extensive walk tests described in the PIR section of this report, additional tests can be 

performed. Slow walk tests are conducted at speeds less than 0.5 feet per second. Most 

volumetric sensors will have a speed at which detection capability decreases. If the potential to 

circumvent a system by crawling is a concern, crawl testing should be performed to obtain 

detection characteristics. The detection pattern of a crawling person will likely be different than 

that of a walking person. 

Performance tests are designed to verify the level of performance of each dual-technology 

sensor through the range of its intended function. Performance testing should be conducted 

when an electronics module is replaced, when there is a change of the physical alignment or 

any adjustment that can affect sensitivity, after remodeling of the building structure, or any major 

change in the arrangement of furniture or equipment. The performance test should include a 

visual inspection of the sensor and of the general area where the sensor is installed. The 

manufacturer’s recommended testing procedures should be followed. 

Within each area being monitored by sensors, the test should (1) ensure that the system meets 

the manufacturer’s specifications for probability of detection, (2) verify that no dead spots exist 

in the zone of protection, and (3) verify that line supervision and tamper protection in both the 

access and secure modes are functional. Records of testing results and equipment sensitivity 

settings or voltage outputs should be maintained so that deterioration in equipment capability 

can be monitored. Walk tests should be performed for all areas covered by the sensor and 

compared with the results of the acceptance test to check for any degradation in the coverage 

of the sensor or misalignment problems. Significant changes in room configuration could affect 

sensor coverage. If room configuration has changed significantly, a complete performance test 

of the sensor coverage should be initiated to ensure asset or room protection. Because the PIR 

is the dominant technology in this configuration, the performance test guidelines described in 

the PIR performance testing section should be followed. These tests should answer the 

questions listed below: 

 Does the sensor sensitivity decrease at higher room temperatures? 

 Can the sensor be covered without generating an alarm? 

 Can a person shield his body temperature from the sensor? 

4.5.6.3 Operability Testing 

The operability testing should consist of a simple walk test and tamper test on each sensor in 

the system. Step tests should also be conducted to verify proper sensor operability. The step 

test is performed starting at likely points of entry and along paths toward protected items or 

areas. 

For example, in the positions numbered 1, 2, and 3 in Figure 56, operational tests are 

performed weekly. Locations 1 and 2 begin at likely points of entry—the door and window. 

Location 3 is an additional test near the door. The alarm stations are contacted before each 

test. The test subject remains still until the alarm station operator signals that the sensor is 
 4-39 

reset and is in the secure state. The test subject takes three steps into the room and stops. 

The alarm station operator verifies that an alarm from the sensor was received from the correct 

location. If any of these simple tests fails to initiate an alarm, the sensor should be checked for 

alignment problems. 

Figure 56: This diagram illustrates the possible walk test locations in a room with sensor coverage by 

a dual-technology PIR-microwave sensor. Note two things: (1) The microwave portion of the sensor 

can penetrate light construction, but since the sensor’s “AND” logic requires that both sensors detect 

before an alarm is registered, a person in the adjoining room won’t cause a nuisance alarm, and (2) the 

tall electrical cabinets block a portion of the sensor’s detection pattern. This could be a problem if the 

electrical cabinets are a possible target and it is possible for an adversary to hide in the location where 

the detection pattern is blocked. 

4.5.7 Maintenance 

A visual inspection of the installation should be performed periodically, particularly after major 

maintenance to the building in the sensor area. Mounting brackets and hardware should be 

inspected for stability and corrosion. Frequent visual inspections ensure that no blocking 

objects have been moved into a position that would render the sensor inoperative. Periodic 

tests, in addition to self-test invoked by the sensor or the system, ensure that the sensor is 

operating effectively. Standby batteries should be replaced on a conservative schedule. Every 

service call should be entered in a log to record the date, time, corrective action, and an 

assessment of the cause of the problem. 

4.6 Video Motion Detection

4.6.1 Principles of Operation 

Video motion detection (VMD) can be added to either analog or digital camera systems. VMD 

has been effectively implemented using daylight cameras, near-infrared cameras, thermal 
 4-40 

imagers, and 360-degree-view cameras. VMD requires the addition of hardware modules 

and/or alarm processing hardware and software. The technology is modular so that it can be 

implemented at either the camera or at the alarm station. In one configuration, VMD software 

can be downloaded into specifically configured digital cameras with embedded digital signal 

processor (DSP) chips and memory so that the detection function occurs at the camera. When 

a VMD detection event occurs, the camera sends an alarm message to the alarm stations and 

then increases the frame rate of the video subsequently transmitted. Prealarm video can be 

stored in the digital camera’s memory, and then the DSP transmits it to the alarm stations when 

an alarm event has occurred. 

VMD technology has experienced significant advances in the state of the art since the early 

2000 timeframe. Lower performance modules are available that provide simple movement 

detection, while higher performing equipment employs sophisticated algorithms to detect and 

categorize a moving target. With the exception of the “object left behind” algorithm discussed 

later, the VMD analysis algorithms are generally activated when movement occurs in the 

camera’s field of view. 

The technology makes decisions about what is moving and the nature of the movement 

occurring in the camera’s field of view. Pixel movements are identified. Then the pixels in 

movement are “blobbed together” as a group of pixels in movement as a group. The blob of 

pixels is analyzed to determine if it falls into the classification criteria needed to generate an 

alarm. Then the motion, direction, and speed of motion (among other factors) are analyzed. If 

the attributes of the motion pass the algorithm analysis tests for being a valid intrusion motion, 

then an alarm signal is transmitted to alarm station’s alarm display, and video of the intrusion 

event is displayed on an alarm station video monitor. 

Early VMD equipment consisted of a module inserted in a camera’s video transmission circuit. 

It highlighted the portion of the video image where motion was detected. Some units highlighted 

an area of the video image when a certain percentage of pixels in the camera’s field of view 

changed. The video processing implemented in these early VMD modules was simplistic and, 

as a result, produced numerous nuisance alarms, thus making the technological enhancement 

not very usable for reliable intrusion detection purposes. Early VMD modules responded to 

essentially anything that moved, including insects walking on the camera enclosure’s front cover 

glass. As the technology advanced, areas within the camera’s field of view could be set as an 

active detection area ignoring movement in all other viewed areas. With increased 

sophistication of activity-related detection algorithms, different portions of the viewed area could 

be made active for different detection events. For example, one area could be set to alarm on 

any movement, while another area could be set to alarm when there was movement from right 

to left and not when the movement was from left to right. 

In recent years, progressive VMD vendors have incorporated significant sophistication into the 

algorithms that analyze motion. Users can calibrate the camera’s field of view with respect to 

object size for purposes of classification, object type determination (human, vehicle), speed, 

size, direction, and location. For example, during camera field-of-view calibration, one approach 

is to have a person stand in the camera’s field of view at three or four locations from near field 

to far field of view. At each location, the operator calibrates the software to an individual’s 

height. For each location, that height calibration information is saved for use by the detection 

and classification algorithms. The analysis software can then accommodate differences in 

object size with respect to location in the camera’s field of view and distance from the camera. 

A human occupies many more pixels in the camera’s field of view when closer to the camera 
 4-41 

than when further away. To compensate, VMD software can scale the detection algorithm’s 

function for identifying human movement throughout the camera’s field of view. 

In some VMD equipment software, it is possible to calibrate the alarm algorithm to allow 

detection of movement at the ground level so that movement that occurs above ground can be 

exempt from classification as an alarm target. That assumes that detection of a person either 

walking upright or crawling on the floor is the target of interest. However, if there is a concern 

about a person swinging into an area on a rope, the robustness of a VMD system’s detection 

algorithm would have to be tested to ensure that the equipment could detect the motion of a 

target in particular size ranges. 

VMD detection and alarm notification are based on a set of “rules” and “areas of interest” 

defined by a system operator. This capability allows specific detection functions to be active 

only within certain portions of the camera’s field of view. The detection function does not have 

to be implemented throughout the entire camera viewing area. For example, if the area of 

interest is inside a large room and there is an aisle for passage through the room alongside the 

area of interest, the intrusion detection function can be configured to be operational for the area 

of interest, while human movement outside the area of interest does not trigger an alarm. 

VMD vendors have established many detection rules for their hardware and software 

configurations. The specific kinds of rules, their functionality, and their reliability vary widely 

from vendor to vendor and from application to application. The technology supplied by a vendor 

of interest should be thoroughly tested in the specific applications envisioned before committing 

to the installation of a particular technology. 

4.6.2 Types of Video Motion Technologies Available 

VMD functionality is available in three configurations: 

(1) Software running on a personal computer with video capture cards 

(2) Stand-alone single- or multi-channel hardware/software modules 

(3) Software embedded within a digital camera with an onboard DSP chip and associated 

memory 

The first configuration is normally at the video head-end located at or near an alarm station. 

Either analog or digital cameras can be connected to the VMD computer, depending on a 

particular vendor’s camera options. The second configuration can be located at either the 

camera or alarm station location. Either analog or digital cameras can be connected to these 

VMD modules. The third configuration is located within the digital cameras at the camera 

locations. 

Some vendors have advanced VMD capabilities to include a tracking function. A movable 

(pan-tilt-zoom) camera is set to view a static scene. When alarm-generating movement is 

detected, the camera moves and zooms in on the target and tracks the target within the limits of 

the camera’s movement and zoom capabilities. The function has been applied to static or 

preset locations in a camera tour of several fields of view, and the tracking function can be 

triggered at any one of the camera’s tour stop locations. At least one vendor has VMD 

equipment with the ability to track movement while the camera is in motion. While the camera is 
 4-42 

panning, the VMD software identifies relative movement within the camera’s field of view and 

then proceeds to track that movement. 

Electrical connection of cameras to VMD equipment is simple and straightforward. Analog 

cameras are connected to a VMD processor using coaxial cable Bayonet Neill-Concelman 

(BNC) connectors, while digital cameras are connected using Ethernet connections to a network 

of high-bandwidth digital switches. High-bandwidth digital networking and trunking to support 

digital video transmission between camera locations and the alarm stations are beyond the 

scope of this discussion. However, it is instructive to note that transmission of high-bandwidth 

video signals is, in many cases, not viable using Ethernet systems designed for message 

transmission such as e-mail and Internet access. Specialized network configuration expertise is 

required for the design and installation of a digital Ethernet network to support efficient and 

reliable high-bandwidth video transmission. 

4.6.3 Sources of Nuisance Alarms in Video Motion Detector Systems 

Commercial VMD technologies have varying degrees of performance; however, performance 

testing of the technology has identified conditions that produce performance challenges. 

Generally speaking, indoor environments tend to produce significantly fewer challenges than do 

outdoor environments. Large changes in lighting conditions, reflections from shiny objects, 

shaking cameras, out-of-focus cameras, a low-contrast scene, a target color near the same 

color as background, a target not occupying enough pixels in the field of view, movement of 

large items in the field of view, such as trees or large birds, and heavy, blowing snow and 

driving rain have been identified as sources of nuisance alarms. Available equipment has a 

wide range of intruder detection and nuisance alarm performance attributes. Therefore, it is 

necessary to thoroughly test the VMD equipment to ensure that the equipment performs to 

expectation before system purchase and installation. 

When used indoors where environmental variables are significantly fewer, VMD technology 

produces significantly fewer nuisance alarms. Indoor lighting in most locations is fairly constant 

throughout the day and generally the camera-to-target distance is much shorter than that 

encountered in outdoor applications. Cameras tend not to shake and vibrate in indoor 

applications, and animals are not present to trigger alarms. 

4.6.4 Characteristics and Applications 

Combining the use of VMD with assessment cameras in indoor applications provides sensor 

functionality without the use of a physical sensor. VMD applications do not have the 

phenomenology associated with a physical sensor to create a detection alarm. The camera and 

VMD software are not sensing the presence of an intruder within a sensored space. Changing 

attributes of a video image are being analyzed by software, and the results of that analysis 

determine if an alarm condition is present. Current video analysis software only approximates a 

portion of the detection and assessment capability of the human mind. While VMD detection 

software has significantly improved since 2000, VMD software is definitely not superior to 

human visual acuity and cognition. However, VMD software does provide surveillance 24 hours 

a day, 7 days a week, to respond to predefined targets and attributes of movement within a 

scene. Humans do not have the capability to continuously focus on a scene for extended 

lengths of time. VMD provides that continuous observation and alerts the alarm station operator 

to allow a human to make the final decision regarding the presence of an intruder. 
 4-43 

As with a physical sensor, VMD provides an indication that there is a change in the area under 

observation when an alarm is generated. The change creating the alarm is visual rather than 

phenomenological. Diagnostic information is also provided to the operator with a VMD alarm 

that is not provided with physical sensor alarms. The VMD software puts a box around the 

identified target in the assessment video to draw the operator’s attention to a particular location 

in the video scene. The operator can then focus on the box in the video to assess what 

triggered the VMD alarm. 

When designing for VMD sensor installation, knowledge of preferential sensitivities associated 

with technology should be understood. The technology is more sensitive to movements across 

the camera’s field of view. Movements toward or away from the camera are less sensitive to 

detection. Movements across the camera’s field of view change more pixels in the image with 

the same amount of movement than does movement towards or away from the camera. 

Therefore, when VMD is used as a detection sensor, the camera should view the scene so that 

the detection pattern is across the camera’s field of view. VMD should not be used with 

cameras that view scenes that experience large changes in scene illumination. For example, if 

a camera is oriented so that it views the inside of an exterior door, opening the door on a bright 

sunny day will cause a large change in scene illumination when the door is opened and may 

either cause a nuisance alarm or nondetection of personnel entry through the door because of 

the significant perturbation presented to the classification and detection algorithms. 

VMD tends to be more sensitive to black pixel and white pixel movements. These colors are at 

the extremes of the color spectrum and less decisionmaking is needed about pixel movement 

as compared to movement of pixels in the middle of the grey scale or with muted colors. 

Because of the sensitivity to white and black pixels, the scene’s area of interest for VMD 

detection must not include an area that experiences moving shadows or moving sun glint. If 

VMD is applied in an area where there are windows (particularly if the windows are facing east 

or west), the low sun angle entering the windows can cause persons to cast shadows inside the 

building. If the area of interest includes an area where moving shadows are cast, this may 

cause unnecessary activation of the detection and classification algorithms creating the 

possibility of nuisance alarms. 

The use of VMD with cameras that shake or vibrate is problematic. From the VMD software’s 

perspective, all the pixels in the camera’s field of view appear to be in motion. This results in 

significant image processing and analysis. If there is by chance some patterned motion within 

the random motion of all the pixels in motion, the detection algorithm will create an alarm 

because, in its analysis, there appeared to be “motion with purpose” in the video stream. 

As described earlier, some VMD software algorithms can adapt to slow scene changes. This 

adaptive response is needed, particularly for exterior applications where outdoor illumination in 

lighted areas may vary by four to five orders of magnitude. Adaptive algorithms can 

compensate for very slow movements. A very determined intruder could gain entry into an area 

with very slow movement. Also, some VMD systems are not sensitive to movements of pixels 

of a color similar to the background color. If this is the case, intruders could cloak themselves in 

fabric of a color similar to the background or floor and very slowly gain access. 

Similarly, if a thermal imager is the video source for VMD analysis, an intruder could insulate 

themselves with highly insulating garments and then cloak themselves under another thick 

insulating material so that the thermal imager does not view movement of a human because 

everything in the thermal imager’s field of view appears to be at the same temperature. In these 

cases, complementary sensors with orthogonal detection criteria would be needed. 
 4-44 

4.6.5 Installation Criteria 

As described in the nuisance alarm discussion above, cameras for VMD should view a detection 

area so that intruder movement is across the camera’s field of view rather than up or down. 

Cameras should be installed so that they are looking at an area of interest at an angle. 

Mounting cameras on a ceiling so that they are looking straight down is problematic for some 

VMD algorithms because looking straight down at the floor causes the top and bottom of the 

camera’s far field of view to be at the same distance from the camera. Algorithms are normally 

expecting that the top of the camera’s field of view be further away from the camera than the 

bottom. 

Scene background should be a neutral color rather than a very light or very dark color. A scene 

with a very light or very dark background color makes it easier for an intruder to blend in with the 

background. 

Cameras for VMD sensors should be installed on solid structures that do not shake or vibrate. 

This minimizes the amount of computations that the VMD algorithms must make and improves 

the ability to detect an intruder. 

For indoor locations, installing visible light cameras with area illumination rather than thermal 

imager cameras is preferable from a detection perspective. 

VMD detection areas should not be implemented in locations where shadows move across the 

detection area. Because of VMD detection algorithm sensitivities, unnecessary alarms can be 

generated by moving shadows in a camera’s field of view. 

VMD cameras should not be installed so that they view the inside of exterior doors. Opening a 

door during bright sunlit days will cause large bright spots in the camera’s field of view, which 

may cause the VMD algorithm to not detect human movement in that area. 

VMD technology should be installed so that it is integrated with either a digital video recorder or 

network video recorder for instant playback of the alarm video. When the camera video images 

are processed through a VMD module or processor before being recorded on digital media, the 

recorded video will be “marked up”; that is, the recorded video will have alarm boxes around the 

area where the VMD camera observed movement. This allows the operator to focus on the 

portion of the video image where movement was detected rather than having to search for that 

location in video that is not marked up. Most VMD cameras can transmit and produce images 

to be monitored at monitoring locations such as alarm stations within 2 seconds from detection 

which is generally an acceptable standard of performance. 

4.6.6 Testing 

Testing a VMD sensor is very similar to testing a physical sensor. Targets of interest move 

through the scene at a range of speeds and at varying aspect ratios. If a human is the target of 

interest, movement includes the following: 

 Walking and running at various speeds 

 Walking and crawling at normal and extremely slow speeds through a VMD camera’s 

field of view to ensure that an alarm is created 
 4-45 

Tests should also include a human doing a belly crawl with a fabric cover that is approximately 

the same color as the background or floor. 

A regular program of testing sensors is imperative for maintaining them in optimal operating 

order. Three types of testing need to be performed at different times in the life of a sensor: 

acceptance testing, performance testing, and operability testing. 

Alarms should be produced deliberately during all types of tests. 

4.6.6.1 Acceptance Testing 

Acceptance testing for the video assessment system is the most encompassing because 

baseline performance and operability are determined and documented. Acceptance tests will 

uncover operational and functionality issues that need to be addressed to ensure system 

operation in accordance with design specifications. Acceptance tests should be performed to 

ensure that the VMD software produces alarm messages in response to tamper or defeat 

attempts. Use the following guidelines for acceptance tests: 

4.6.6.1.1 Testing the Camera-to-Alarm-Station Connection:

(1) Ensure that each camera produces a VMD video image on the monitor. 

(2) If camera images have graphic legends displayed on the monitor, ensure that the 

graphic legends are labeled correctly for the VMD camera channel being tested. 

(3) Ensure that VMD intrusion alarms in assessed areas trigger the appropriate camera’s 

video to appear on the alarm station monitor. For example, an individual in the field 

communicating with an individual in the alarm station using a two-way radio triggers an 

intruder alarm in each VMD-sensored zone and ensures that VMD video resulting from 

the alarm has a box around the intruder and is from the correct camera for the zone in 

alarm. This individual also ensures that the assessment video appears on the alarm 

station monitor within the timeframe as specified by the manufacturer (2 seconds is 

generally an acceptable standard) and the playback of recorded video is from the correct 

camera. 

4.6.6.1.2 Testing for the Correct Error Message by Simulating Potential Problems:

(1) Disconnect power to individual cameras at field camera junction boxes, and ensure that 

a VMD “loss of video” alarm occurs for the camera disconnected. 

(2) Cover the front of camera enclosure with a black plastic bag or densely woven cloth, and 

ensure that a VMD “loss of video contrast” alarm occurs for the camera tested. 

(3) Shine a bright light into the front of each camera, and ensure that a VMD “loss of video 

contrast” alarm occurs for the camera tested. 

(4) Turn off the lights in the area viewed by the camera to produce a dark, low-contrast 

image, and ensure that a VMD “loss of video contrast” alarm occurs for the camera 

tested. 
 4-46 

(5) Disconnect the video signal cable from each analog camera, and ensure that a VMD 

“loss of video” alarm occurs for each camera channel disconnected. 

(6) Disconnect the fiber-optic video transmission cable (fiber) for each camera, and ensure 

that a VMD “loss of video” alarm occurs for the camera channel disconnected. 

(7) Physically move or rotate the camera so it is no longer viewing the intended scene, and 

ensure that it generates an error message. 

4.6.6.1.3 Testing for Proper Ethernet Connections:

(1) Disconnect the Ethernet cable from each digital camera, and ensure that a VMD “loss of 

video” alarm occurs for the camera channel disconnected. 

(2) Disconnect the camera Ethernet cable to Ethernet switches carrying video signals, and 

ensure that a VMD “loss of video” alarm occurs for all cameras connected to the switch. 

(3) Disconnect the power cable to Ethernet switches connecting video signals to the VMD 

hardware, and ensure that a VMD “loss of video” alarm occurs on all camera channels 

connected to the switch. 

4.6.6.1.4 Testing for Multiple Intrusion Alarms in Multiple Zones:

(1) Simultaneously create intrusion alarms in two, three, four, and five adjacent and 

nonadjacent perimeter zones, and ensure that the alarm assessment video queues up 

the recorded (prealarm) video and that the recorded video is displayed for each of the 

alarming zones. 

4.6.6.2 Miscellaneous Testing 

In areas where sunlight enters the area, during daylight periods, an observer should ascertain 

that alarms are not created as the sunlight and the shadows it creates moves across the VMDsensored area. Also under the same conditions, an observer should ensure that shadows 

created by persons walking adjacent to VMD-sensored areas do not create alarms. 

At six-month intervals, secondary power source operation should be tested by disconnecting the 

primary power source to the security system and ensuring that the security system continues to 

function without creating detection alarms or system failure. 

4.6.6.3 Performance Testing 

VMD performance is also affected by the issues indicated in Section 4.6.7.4, “Operability 

Testing.” However, performance degradation is usually caused by changes of lower severity in 

the issues noted above. Usually, the performance or functionality degrades but the functionality 

does not cease completely. Physical changes in the baseline scene will also affect VMD 

performance. For example, if a piece of furniture or equipment is permanently added or 

removed from the scene, the baseline scene must be recalibrated to reset the detection 

algorithms to the new baseline condition. Some VMD software readily adapts to changes in the 

baseline scene over some period of time. However, to ensure proper performance, a manual 

recalibration of the camera viewing the changed scene should be performed. 
 4-47 

To optimize digital network bandwidth utilization, digital video processing at the camera 

generally involves video image compression. Video compression reduces scene resolution to 

minimize the amount of information transmitted from the camera to the alarm station. The 

amount of compression applied affects the amount of fine detail taken out of the video images. 

Application of greater than 20-percent compression begins to significantly affect fine detail in the 

transmitted image. Performance degradation with increased compression is noticed initially at 

the camera’s far field of view and, as compression is increased, that degradation begins to 

affect more and more of the camera’s scene toward the camera. Compression causes the 

edges of objects to become fuzzy. Because VMD software analyzes the edges of groups of 

pixels in movement, compression that causes images to become fuzzy significantly complicates 

and degrades the functionality of the algorithm analysis. 

4.6.6.4 Operability Testing 

VMD operability issues are generally a result of camera degradation or failure, video 

transmission system degradation or failure, video system power or secondary power source 

failure, system grounding or ground loops, or the result of lightning-induced events. 

Operability issues can also result from changes to the detection rules for a VMD scene or 

changes to the VMD calendar or time clock scheduler. 

Physical changes affecting VMD operability include out-of-focus camera; camera moved from its 

initial VMD calibrated position; loss of scene contrast; degradation or failure of camera 

electronics; loss of, or significant change in, area illumination; or bright light appearing in the 

camera’s field of view. 

4.6.7 Maintenance 

Specific maintenance for VMD should focus on maintenance of the camera and video 

transmission system. Because the heart of a VMD sensor is essentially software that analyzes 

camera video, it is anticipated that the software will be undergoing continuous upgrading as the 

state of the art for this technology advances. Therefore, it is anticipated that the VMD software 

may require updates during the life of the VMD sensor. 

The camera lens and enclosure front cover glass should be cleaned and the lens focus 

adjusted, as necessary. 

On a yearly basis, each camera’s image output should be viewed at both alarm stations to 

ensure that the picture is clear and crisp and is not washed out or of low contrast. The absence 

of a clear, crisp picture would indicate degradation in the camera’s electronic circuitry, or in the 

case of analog cameras, it could indicate degradation in the video transmission network or video 

amplifier modules. 

In addition, the tests shown above in the section on acceptance testing should be performed to 

ensure that all the alarm security features are still active and operate properly. 

Uninterruptible power supply batteries for modules providing backup power to the security 

system should be replaced at 3-year intervals.
 
 5-1 

5. WATERBORNE SENSORS 

5.1 Waterborne Sensor Systems

This section provides information about waterborne sensors for facilities with water intakes, as 

illustrated in Figure 57. 

Figure 57: An example of a fiber-optic grid covering a water intake channel. 

5.1.1 Principles of Operation 

A common application for intrusion detection in a waterbourne environment is the use of fiberoptic grid sensors. Fiber-optic grid sensors can be made to accommodate various waterbourne 

applications and configurations with minimal impact to the operational capabilities of the 

structures or systems to which it is attached. When evaluating the detection capabilities of fiberoptic grid sensors, the security industry measures quality by sensing bends and breaks in fiberoptic grids. Typical security configurations use single-mode diameter fiber illuminated with 

approximately 1,500-nanometer (nm) wavelength light, but any fiber diameter or signal 

wavelength are acceptable as long as bends and breaks can be sensed quickly (typically within 

a few seconds or less, but the minimum requirement depends on the overall security system 

configuration). Maximum fiber length typically is a few kilometers, but some vendors claim 

maximum lengths of many times that. What constitutes a “bend,” resulting in signal attenuation 

without total signal loss, will depend on characterization of potential nuisance alarms (e.g., if the 

fiber commonly bends in a strong wind, that will result in more typical attenuation than a fiber 

run indoors, and the sensing system should be adjusted accordingly). 

Once the fiber grid is arranged to ensure that an adversary must break it to enter the facility 

being protected, the fiber is connected to sensing electronics. These electronics check fiber 
 5-2 

continuity, providing an optical signal into the fiber and measuring its output on the other end 

and ensuring that the signal is not greatly attenuated or removed altogether. Some sensing 

systems are capable of detecting where in the fiber line the event is occurring, in addition to the 

event itself, but this capability costs more and is often not necessary for adequate protection. 

Most fiber sensing systems will close or open a dry contact closure relay upon sensing a bend 

or break event, but output is adjustable depending on application needs. 

Fiber-optic cable is especially preferred by security professionals from a tampering perspective 

as its modification requires very specialized tools and delicate procedures. Electrical wire, on 

the other hand, typically just needs a few clips and an extra loop of wire to create enough slack 

to penetrate without detection. 

5.1.2 Types of Fiber Grid Available 

In protecting an area or surface, several vendors have had success creating fiber nets, and 

some have embedded the fiber in a plastic or metal grate for added strength. The increased 

rigidity adds confidence that any break in the fiber is intentional, not accidental or caused by the 

environment. 

 A fiber net can be easily wrapped around an object or surface being protected, or 

stretched taut across an opening that needs to be controlled. Because of its flexibility, 

fiber net is easier to disturb and bend, requiring very little force to cause an intrusion 

event. 

 A fiber grate is a rigid structure typically installed across openings to be controlled, and 

any break or bend sensed is almost always caused by destruction of the surrounding 

medium; the fiber detects that the rigid structure is being breached. 

Both types can be treated to prevent biofouling (underwater growth including algae, barnacles, 

or simple electrochemical corrosion) if deployed in a marine environment. (See Figure 58.) 

Figure 58: This fiber-optic grid was tested under water for about 6 weeks and shows biofouling through 

barnacles, which can eventually degrade the integrity of the materials. 
 5-3 

5.1.3 Sources of Nuisance Alarms 

Of the two major types of fiber grid, the more flexible fiber net experiences multiple nuisance 

alarms in a marine environment. Marine mammals are often inquisitive and can bump the net, 

which results in enough signal attenuation to cause an alarm. A strong water current flowing 

through the net can distort it, also causing an alarm. The sensing system threshold can be 

adjusted to allow these types of events, but at the cost of possibly not sensing actual malicious 

bending and stretching of the net. Also, exact characterization of marine mammal interference 

is difficult. 

The fiber grate, a much more rigid structure, is typically considered free of nuisance alarms. 

5.1.4 Characteristics and Applications 

The fiber net can be used on a shaped surface that needs to be protected, an odd-shape 

opening that needs to be protected quickly, or a location where weight is a major consideration. 

A fiber net can also detect activities such as climbing and is, in general, more responsive (than 

a grate) to environmental influences. Fiber nets work well for detection of several types of 

events (i.e., pushing, climbing, gathering, cutting, and others). A net is relatively cheap and 

easily replaced. 

A metal or plastic fiber grate creates delay (as long as an alarm is generated) and strong access 

denial and works where the primary activity to be sensed is cutting. Because a grate is a rigid 

structure, a single cut does not grant access but will sound an alarm, which allows notice of 

malicious activity before adversaries are able to pass through the barrier. A “smart fence” can 

tell when someone has broken through it, and it can be manufactured in any reasonable size. 

The following characteristics apply to fiber nets: 

 Fiber nets are weaker than grates and are more vulnerable to damage in turbulent 

environments or where heavy debris could be carried into them. 

 Fiber nets can be slashed, so swimmers are able to pass through the net immediately. 

 Fiber nets can be “noisy” (have frequent nuisance alarms) caused by underwater 

currents flowing against them or from marine mammals bumping up against them. 

The following characteristics apply to fiber grates: 

 Fiber grates are inflexible, so if a swimmer were to cut the grate free from its support 

structure, it could be completely lifted away without an alarm being sensed (adding 

antitamper devices can mitigate this problem). 

 Fiber grates can corrode quickly if metal grates are not installed correctly (with a zinc or 

magnesium sacrificial bar, which must also be maintained and/or replaced during the life 

of the grate). 

 Plastic fiber grates can embrittle. Low temperatures and exposure to ultraviolet light can 

embrittle plastic grates. 
 5-4 

The following characteristics apply to both fiber nets and grates: 

 Fiber grids are susceptible to biofouling, resulting in corrosion and damage. Organisms 

such as barnacles could restrict water flow through a grate. 

 Regular cleaning may be necessary to prevent interference from barnacles. (See Figure 

58.) Anti-biofouling paints are effective against organisms adhering to the grate but are 

usually toxic to the environment. 

 Fiber grids require assessment to confirm an alarm. 

 Fiber grids are difficult to service underwater. 

5.1.5 Installation Criteria 

When installing either fiber grid system, it is necessary to work closely with the manufacturer to 

ensure that all potential problems are mitigated. Installation criteria include the following: 

 Install a sacrificial zinc or magnesium block on metal components. 

 Test plastic material in the ultraviolet lighting conditions or temperature ranges 

experienced in the location to be installed. 

 Use anti-biofouling coatings (if the wildlife in the area will not be affected) and determine 

cleaning methods and schedules. 

 Add tamper-indicating conditions to ensure that the grate or net cannot be defeated 

without causing a tamper alarm or from being circumvented completely. For example, 

ensure that it is difficult to make a new opening next to a secure opening. 

5.1.6 Testing 

A regular program of testing sensors is imperative for maintaining them in optimal operating 

order. Three types of testing need to be performed at different times in the life of a sensor: 

acceptance testing, performance testing, and operability testing. 

5.1.6.1 Acceptance Testing 

Acceptance testing should answer the following questions: 

(1) What is the vendor’s prediction for long-term survivability of the grid? While some 

corrosion or decay is expected over time, will the grate or net degrade in a timeframe 

that is acceptable to the facility? 

(2) What strategies will be employed to prevent biofouling? Will the grate or net become 

overgrown with algae or barnacles? 

(3) Could the grate or net be accidentally damaged, and what strategies will be used to 

prevent accidental damage? 
 5-5 

(4) What is the projected maintenance or replacement schedule and what are the 

associated costs? 

(5) What are the tamper-indicating strategies employed for the grid? Does the system 

alarm when fiber is unplugged? Testers should simulate a fiber disconnection instead of 

actually unplugging the fiber because the fiber connector ends must be cleaned before 

re-connecting. 

(6) What is the acceptable threshold to prevent frequent nuisance alarms? Does the 

system alarm if the grate or net is rattled or hit? 

(7) Does the grid respond to a break? Work with the manufacturer to simulate breaking the 

grid (either grate or net) to generate an alarm instead of actually breaking the materials. 

5.1.6.2 Performance Testing 

Performance testing should be done regularly to ensure that the system meets performance 

criteria, as follows: 

(1) To ensure that the system will not report frequent nuisance alarms, shake or hammer 

the grid to simulate a marine mammal or water current interference and ensure that no 

alarm is sensed. 

(2) Based on the manufacturer’s recommendation, simulate breaking the grid (either grate 

or net) to generate an intrusion alarm instead of actually breaking the materials. 

5.1.6.3 Operability Testing 

Operability testing ensures that the system works as intended. Operability testing for fiber-optic 

grids involves nondestructive testing. Since the primary event to be sensed is cutting, the 

primary test will follow the vendor’s prescribed methods to simulate cutting. 

5.1.7 Maintenance 

Maintenance should be performed according to a defined schedule. If performance or 

operability testing shows degraded system performance, the maintenance schedule should be 

adjusted accordingly. The following maintenance is recommended (if not already required by 

the vendor): 

 Clean the grid, or verify that there is no growth on the grid. 

 Clear any debris from the grid mesh. 

 Check for corrosion around signal lines, connectors, and the sensor structure.

 6-1 

6. VIDEO ASSESSMENT 

6.1 Video Assessment Systems

6.1.1 Overview 

Assessment is a critical component of detection and is equally important to the initiation of 

response. Assessment provides a means to determine the necessary actions (responses) 

needed to mitigate situations that pose a challenge to physical security. The key element within 

the assessment process is identification. Identification assists the security force in selecting 

appropriate responses within a force continuum to address security-related and potential threat 

situations resulting from the detected activity. Likewise, identification provides a means for the 

security force to determine the absence of a threat resulting from detected activity such as a 

nuisance alarm caused by wildlife or debris. It is equally important that the assessment 

techniques identify the stimulus that caused the alarm quickly, before the stimulus of the alarm 

disappears from view. This enables the initiation of timely response consistent with the goals 

and objectives of the physical protection program and protective strategy. Therefore, video 

assessment systems should be robust and capable of providing the highest level of protection 

for the specific application in which they are employed. 

6.1.2 Principles of Operation for Video Alarm Assessment Systems 

A video alarm assessment system allows security personnel to determine rapidly, after a sensor 

alarm, if an intrusion has taken place within the facility. In addition to real-time observation of 

the location where the sensor alarm occurred, the video assessment system can record and 

store video of alarm events and other significant event information. This permits retrieval of 

event images within the protected area, even under conditions of multiple simultaneous alarms 

or delayed security personnel attention. 

The design of the video assessment subsystem should consider the following goals: 

 Ability to completely assess all sensor locations 

 Ability to assess nuisance alarm sources 

 Ability to provide system response fast enough to assess the area before the intruder 

leaves the area 

A video alarm assessment system consists of cameras at sensored areas that display video 

images on monitors in the alarm stations, video switching, and recording and communication 

systems for transmission of the video images from the cameras to the alarm station monitors. 

Figure 59 and Figure 60 show block diagrams of analog and digital alarm assessment system 

components. The major components of the video assessment system include the following: 

 Cameras and lenses to convert an optical image of an assessed scene into an electrical 

signal 
 6-2 

 A lighting system to illuminate isolation zones evenly and sufficient intensity to produce 

usable video images of assessed areas at night 

 A video transmission system that connects the cameras to the alarm station switchers 

and monitors 

 A video switching system that takes the video from cameras and routes it to recording 

and monitoring display devices 

 A video recording system that records video from camera feeds for archival needs or 

alarm event recording 

 Video monitors for display of alarm assessment video 

 An alarm communication and display controller to interface between the alarm sensor 

system and the video alarm assessment system to display video in the alarm stations 

when a detection sensor detects activity and produces an alarm 

LIGHTING

CAMERA

Transmission System

Video Conditioning System

Video

Switcher

Controller

Video

Recorder

Alarm

Interface 

video video

video

data

CAMERA

data

video

data

video

video Monitor

Monitor

LIGHTING

CAMERA

Transmission System

Video Conditioning System

Video

Switcher

Controller

Video

Recorder

Alarm

Interface 

video video

video

data

CAMERA

data

video

data

video

video Monitor

Monitor

Figure 59: Diagram of an analog video system. 
 6-3 

LIGHTING

Network Server

Database

Network VIDEO

RECORDER

Network 

Access control

Alarm Interface

IP interface

to Analog Camera

Network transmission 

system (Fiber, copper, 

wireless

Network Data

Network-Based

Video System

IP-Addressable 

Cameras

Work 

Station 

Monitor

LIGHTING

Network Server

Database

Network VIDEO

RECORDER

Network 

Access control

Alarm Interface

IP interface

to Analog Camera

Network transmission 

system (Fiber, copper, 

wireless

Network Data

Network-Based

Video System

IP-Addressable 

Cameras

Work 

Station 

Monitor

Figure 60: Diagram of a network-based digital video system. 

A camera converts the physical scene in the camera’s field-of-view into an electrical signal 

suitable for transmission over a cable, fiber, or wireless media to a video monitor for viewing by 

an observer and digital video recording for playback and archival information. The video 

switcher directs the signal to a selected monitor for display of the visual scene observed by the 

camera. A selected signal can also be routed by the video switcher to and from a video 

recorder for playback of pre- and post-alarm video and for permanent archiving and forensic 

analysis. 

Camera resolution, sensitivity, lens field of view, and aperture should be considered during the 

design of exterior perimeter isolation zone lengths and widths. Each video assessment system 

aspect should be considered individually and within a system. If assessments need to be made 

from recorded data, then the resolution of the recording device should be considered. To 

compensate for reduced video recorder playback resolution, reduced spacing between cameras 

and reduced maximum assessed area lengths may be required. The video recording and 

storage device may be the resolution-limiting factor in the assessment system. If video 

information is to be retrieved from archive recording, then the archive recorder resolution should 

be considered in the system design. 

Additional assessment cameras, associated circuitry, and hardware must be installed if sensor 

zones need to be shortened by terrain variations or locations of personnel access points. Each 

sensor zone should be evaluated individually to ensure that appropriate assessment equipment 

is installed and assigned to provide optimal performance of assessment capabilities within the 

isolation zone. It is more beneficial to install multiple assessment cameras in an extremely long 

sensor zone than risk a reduced or limited assessment capability and thus reduce the overall 
 6-4 

level of protection provided by the intrusion detection and assessment system. Sensor zone 

width also has an effect on the maximum assessment zone length; narrower widths allow 

assessment of longer zones. 

Most of the head-end video assessment equipment can be located in or near an alarm station 

for convenience, a temperature-controlled environment, and ease of access for maintenance. 

Normally, only the cameras, towers, power supplies, video transmission equipment, and signal 

transmission media are located external to the alarm stations. 

6.1.3 How Lighting Affects Camera Sensitivity and Resolution 

Camera sensitivity must be considered when designing the lighting system. A high-resolution 

camera will not function properly if the illumination is inadequate. The lens relative aperture 

(i.e., f-stop) must be considered in these determinations. Generally, faster lens speeds (lower 

f-number) are selected when more than one option is available, even if a lens with a lower 

f-number is somewhat more expensive. Lenses with f-numbers higher than f/1.8 should not be 

used except under very unusual circumstances. Lenses with f-numbers higher than f/1.8 will 

require increased lighting levels or a more sensitive camera. 

A camera’s sensitivity or performance under low light conditions often cannot be judged from 

manufacturers’ specifications alone because a common standard does not exist. Some 

manufacturers reference scene illumination levels or illumination levels at the camera’s imager 

that do not represent camera performance in security applications where a lens and its aperture 

affect the amount of light appearing on the camera’s imager. These variant light levels are 

subjective and therefore do not allow performance comparisons. A side-by-side evaluation of 

cameras operating in the intended environment is the preferred way to determine a camera’s 

suitability for assessing a particular area. 

For a scene to be visible to the camera, it must be illuminated by sufficient natural or artificial 

light and must reflect a portion of that illumination for observation by the camera through a lens 

with appropriate field of view for assessment purposes. The light reaching the lens must then 

be clearly focused onto the camera’s light-sensitive imager surface and converted into an 

electrical signal by the camera electronics system for transmission to the alarm stations. 

6.1.4 Concepts of Cameras Used in Video Assessment 

The most efficient use of assessment cameras is achieved when smaller camera imager size 

and longer focal length lenses are used. To the extent that these factors can be optimized, the 

number of cameras, towers, and camera subsystem infrastructure video transmission system 

components can be minimized. Longer focal length lenses have narrower fields of view. This 

minimizes the amount of area outside the perimeter being viewed. Assessment cameras can 

view more than one sensor zone in some circumstances. If a video assessment system is 

judiciously designed, when a camera outage occurs, an adjacent zone’s camera may have the 

capability to assess a neighboring zone until that zone’s camera is operational again. 

Alarm assessment using video technology employs cameras and lenses installed in camera 

enclosures and accessory equipment to create video images for an operator to observe in a 

facility’s central alarm station (CAS) or secondary alarm station (SAS). Cameras are 

manufactured to widely varying requirements, performance standards, quality levels, and 

reliability. 
 6-5 

Analog security cameras are an offshoot of broadcast television technology; they are designed 

to provide a video output signal that is almost identical to that of an analog television camera. 

Currently, many analog camera vendors offer a wide range of camera technologies at widely 

varying prices. As camera technology advanced, the digital video camera became available. 

Many digital cameras are available to implement assessment systems using digital camera 

technology and digital video transmission systems. 

The camera’s electrical video signal is carried by a transmission media coaxial cable or 

fiber-optic cable to the alarm stations where it is displayed on a video monitor for viewing by an 

operator. Analog cameras produce an analog output signal in a specified format for viewing on 

a picture-tube-type or flat screen digital monitor. Digital cameras are connected to a computer 

network and provide a signal to the alarm stations through the network via a stream of digital 

packets similar to the process that produces video on a desktop computer. 

6.1.5 Testing Video Assessment Systems 

The testing portions of this section contain testing information that should be approached from a 

systems point of view. The testing section addresses several kinds of testing, including 

acceptance, operational and performance testing, integrating cameras, digital video recorders 

(DVRs), lighting, and system elements. 

6.2 Cameras

6.2.1 Principles of Operation 

Depending on the specific camera imager technology implemented, camera imagers respond to 

visible and near-infrared illumination or thermal signatures of targets within the camera’s field of 

view. Camera placement depends on appropriate lens selection to adequately assess a defined 

area, zone, or sector. Detection sensor area and camera field of view area must be coincident. 

If a camera’s field of view does not completely encompass a sensor’s detection area, additional 

cameras must be deployed to ensure that all of the detection area can be observed with the 

video assessment system. Similar to motion picture format, a video picture comprises 30 still 

pictures per second taken in succession, compared to 24 still pictures per second in motion 

pictures. Each picture is called a frame. 

Cameras have six distinct categories: black and white, color, day/night, infrared and infrared 

enhanced black and white, intensified, and thermal. Cameras with different technologies can be 

used together to provide a wide assessment capability for specific applications. This is 

particularly true when assessment must be performed in extremely low light conditions of less 

than 0.01 f-c (0.1 lux). For example, in unlit areas, a color camera can be used during the day 

and a thermal imager camera used at night. 

The heart of a camera is a solid-state imager. The imager has a pixel array that converts light 

energy to an electronic charge. The performance of imager technology is affected by factors 

such as resolution, sensitivity, color versus black and white, and infrared or thermal spectrum 

sensitivity. The resolution of a quality analog color camera is approximately 470 lines. The 

resolution of a quality analog black and white camera is approximately 570 lines. Digital 

cameras have 520 to 4,000 lines of resolution. Infrared-enhanced camera imagers can provide 

video images appropriate for video assessment with low-power infrared illuminators. Thermal 

imagers have a range of 160 to 480 lines of resolution. 
 6-6 

6.2.1.1 Camera Resolution 

Resolution is the degree to which one can see fine detail in a viewed image. It is also a 

measure of spatial frequency or the number of pairs of alternate black and white evenly sized 

lines that can be seen in a given linear distance, typically expressed in line pairs per millimeter. 

The line pairs designation is used primarily in the field of optics, but the term also appears in 

television literature. Different camera resolution charts have been developed for color and for 

black and white cameras. Figure 61 shows examples of both color and black and white 

resolution charts. 

Camera resolution is measured using a resolution chart where groups of equally spaced black 

and white lines arranged in a wedge-shaped pattern form the basis for resolution measurement. 

As shown in the left picture of Figure 61, the chart is normally calibrated for horizontal resolution 

between 200 and 1,600 horizontal TV lines (HTVL). The units of measure are stated as either 

horizontal or vertical TV lines. Vertical resolution is fixed by the scan rate. A color camera 

resolution chart is shown at right. 

 

Graphic courtesy of CCTV Labs, www.cctvlabs.com 

Figure 61: Examples of laboratory black and white and color camera resolution charts. 

As horizontal resolution increases, finer detail can be observed in the image. To determine 

camera resolution, a camera is positioned so that it views the full chart with no background 

visible (see Figure 62). When positioned correctly, the little arrows at the edge of the resolution 

chart align with the edge of the monitor viewing area. Observing the video monitor, at some 

point along the vertical converging black and white lines, the lines merge. At this point, four 

distinct black and white transitions can no longer be discerned. The point where the lines barely 

appear separate is the horizontal resolution. The resolution in HTVL is read from the numbers 

on the chart. For example, if four distinct lines are no longer visible at a point a quarter of the 

way between the 500- and 600-line calibration points, the camera would have a 525-line 

horizontal resolution. Figure 63 shows examples of field resolution charts. 
 6-7 

Figure 62: Example of a resolution chart test setup. 

 Rotakin is a registered trademark of The Home Office

Figure 63: Examples of field resolution charts (Rotakin at right). 

As a point of reference, for real-time assessment, the horizontal resolution of a good quality 

video camera is about 800 pixels. Historically, 1 percent, or 8 pixels per foot of horizontal object 

resolution has been used as a basis for the resolution needed for intruder classification. This 

indicates that the maximum horizontal field-of-view should be limited to 30.5 meters (100 feet). 

It is important to note that object resolution specification in pixels per foot must encompass all of 

the camera-to-monitor elements (e.g., camera, lens, transmission system, video recorder, and 

monitor) to determine the video assessment system’s end-to-end resolution. 

For purposes of alarm assessment, three levels of resolution need to be considered: 

(1) Detection—Ability to detect that an object is present in the camera’s field of view; 

however, exact identification of the object may not be possible (see Figure 64). 

(2) Classification—Ability to determine whether the object in the camera’s field of view is 

human or nonhuman (see Figure 65). 
 6-8 

(3) Identification—Ability to determine the unique identity of the human in the camera’s field 

of view based on details of appearance (see Figure 66). 

Figure 64: Example of video image showing detection. 

Figure 65: Example of video image showing classification. 

Figure 66: Example of video image showing identification. 

These three levels of resolution are dependent on the camera’s resolution and the size and 

proximity of the object to the camera. For example, depending on camera resolution, object 
 6-9 

size and object distance from the camera, it may be possible to identify a particular person, 

classify an object such as a large dog, or detect an object the size of a small animal. 

Consideration of the object or assessment target is critical in determining camera placement 

and the number of cameras required. In an exterior perimeter situation, a security system 

operator may need to classify a person crawling slowly through an assessment zone at night. 

The person crawling could be close to the camera or at the camera’s far field of view. 

The distance from the camera to the assessed area’s far field of view is limited by a design 

criterion requiring that a specified number of lines of resolution (and thus a number of horizontal 

imager pixels) are occupied by a certain sized target. The amount of resolution required is 

determined by the level of assessment needed at a particular camera location. When 

assessment requirements change from intrusion detection to classification to intruder 

identification, the number of lines or pixels that a target must occupy on a video monitor screen 

increases. 

Table 1 shows the number of horizontal pixels that are required for the three levels of 

assessment. In high-resolution camera imagers, the relationship between pixels and HTVL is 

0.75. For example, it is recommended for assessment classification of a human intruder that 

there be eight horizontal pixels on a 1-foot target. From above, eight pixels equal six HTVL on a 

1-foot target. With eight pixels or six HTVL on a 1-foot target at the camera’s far field of view, 

the resultant picture quality allows the security system operator to be able to recognize and 

discriminate between human and animal.

Table 1: Assessment Type and Required Pixels

Assessment Type Pixels 

Detection 2 to 3 

Classification 6 to 9 

Identification 10 to 16 

Distance from the camera, camera resolution, lighting, and other video assessment system 

performance characteristics contribute to how easily and quickly an operator can assess a 

situation. For exterior perimeter applications, having a camera resolution that allows an 

operator to classify a target is most likely sufficient to differentiate between an adversary attack 

(crawling persons) or a nuisance alarm such as a rabbit or crocodile. At the other extreme, for 

some interior applications, it may be desirable to uniquely identify a human in the camera’s field 

of view. 

6.2.2 Types of Cameras Available 

This section provides an overview of camera technologies available for use in video assessment 

applications. Topics cover generic camera classifications such as color, black and white, and 
 6-10 

thermal, as well as technical attributes of some cameras such as auto shutter, auto iris, and 

integrating types. 

6.2.2.1 Color and Black and White Cameras 

While a color camera enhances daylight scenes by providing additional color information about 

the target being assessed, nighttime use of color cameras, particularly when a scene is 

illuminated with high-pressure sodium (HPS) lamps, can be problematic. Security perimeter 

field tests of color cameras with HPS lights have not been favorable. At night, HPS lamps 

cause a gold-orange color to appear on monitor images; for example, a perimeter floor 

composed of light-grey, rounded river stones appears orange. At maximum distances, it is 

difficult to distinguish an intruder’s exact clothing color under the varying lighting conditions 

encountered in locations illuminated with HPS lamps. To the human eye, HPS illumination can 

distort naturally occurring color cues. 

When comparing color and black and white cameras with the same type of camera imager, 

color camera resolution is about 18 percent less than that of an equivalent black and white 

camera imager. The black and white camera provides a brighter, sharper, higher-contrast 

image at night because of its higher resolution and operation only in the grey scale. More 

discussion is contained in the “Day/Night Cameras” section. 

6.2.2.2 Day/Night Cameras 

Some cameras produce color images during the day and black and white images at night, 

taking advantage of the best features of both. The camera has a sensor that measures the 

ambient light level and controls switching from day to night mode. On some day/night cameras, 

the ambient light level at which the switchover occurs can be adjusted. The camera electronics 

monitor the output video level and switches from color to black and white when the scene 

illumination level is less than a predetermined level. When transitioning from day to night mode 

(color to black and white mode), the camera mechanically removes a near-infrared filter. With 

the camera in the black and white mode, it then responds to near-infrared illumination blocked 

by a filter during the day. Removing the filter also improves picture brightness. This increases 

the amount of scene illumination reaching the camera imager. The nighttime black and white 

image has approximately 18 percent more resolution than the daytime color image. 

6.2.2.3 Electronic Shutter Cameras 

The pixels in camera imagers can be likened to electronic capacitors. Instead of accumulating 

electrical charge as capacitors do, camera imager pixels accumulate light charges over an 

active charging time and then send that charge information to be processed into a complex 

electronic signal for the monitor to display. Some cameras adjust the amount of time that the 

camera imager is allowed to be exposed to a scene for producing a frame of video. These 

cameras have electronics that automatically adjust the amount of imager exposure time as a 

function of scene illumination level. Exposure time is very short during sunny environments and 

is lengthened in darker nighttime environments. 

6.2.2.4 Integrating Cameras 

When scene illumination is too low and grainy pictures occur, some camera models can 

increase the time over which camera imagers are exposed to the scene. Known as integrating 
 6-11 

cameras, the length of time that the imager is allowed to be exposed to incoming illumination is 

increased to make the image brighter and improve scene contrast. These cameras slow the 

shutter speed to greater than 1/30th of a second when viewing very dark scenes to obtain 

enough scene illumination to produce a picture with sufficient contrast for assessment purposes. 

Some cameras can slow the shutter speed to as long as 4 seconds, but that length of time 

between frames is too long for adequate assessment. Integrating light for longer periods of time 

causes moving images to become blurred. For good assessment, the shutter speed should not 

exceed 1⁄4 of a second. An intruder running a 4-minute mile will traverse 1.7 meters or 5.5 feet 

in 1⁄4 of a second. 

6.2.2.5 Intensified Low-Light Cameras 

In a camera that has an intensifier component, photons are linearly accelerated and bombard a 

luminescent (green) screen. A color camera is focused on the green screen to create the 

displayed video signal. The intensifier responds to near-infrared illumination from stars, the 

moon, and artificial lighting. These passive cameras are only light receivers and do not emit 

near-infrared energy to illuminate the scene. The intensifier requires replacement and 

maintenance and has a limited life on the order of 2,500 to 3,500 hours of operation. Bright light 

sources in the scene can create washout smears or streaking in the camera image. 

6.2.2.6 Thermal Imager Cameras 

The thermal imager camera converts thermal radiance to a video signal. Its camera video 

output can be a black and white image showing the temperatures of objects as shades of grey 

or in a gradation of colors calibrated to temperature bands. Thermal camera imagers have 

resistive element pixels that respond to thermal/infrared energy in the 3 to 5 or 7 to 14 micron 

waveband emitted from warm-bodied sources. A thermal camera is a night vision device that 

responds to differences in temperatures against a background temperature reference. A 

thermal camera is a passive device and requires no illumination to produce a video image. The 

picture displayed is based on the difference in temperature of objects in the scene. Cooled 

thermal imager cameras typically use nitrogen cooling loop Sterling pumps. The advantage of 

cooled thermal imagers is that they have higher sensitivity to small changes in temperature. 

The Sterling pumps, however, require replacement at 10,000- to 15,000-hour intervals. 

6.2.2.7 Pan-Tilt-Zoom Camera 

The pan-tilt-zoom (PTZ) camera provides alarm station operators a level of versatility in 

performing surveillance tasks not possible with the use of fixed cameras. With a PTZ camera, 

the operator can rotate the camera over a 360-degree field of view, move the camera up and 

down, and zoom in to more closely observe activities of interest. PTZ cameras come in a range 

of mechanical configurations, including an exterior mount, dome-type camera; an exterior-mount 

camera configuration with fixed cameras mounted on an integrated pan-tilt mechanism (lenses 

can be fixed or zoom); an enclosed, ceiling-mount dome indoor camera, and a nonenclosed 

indoor camera. 
 6-12 

6.2.3 Concepts for Cameras 

6.2.3.1 Imager Format 

The camera’s format designator is based on the size or format of the image device. The 

camera format is related to the size of the photosensitive surface and is a measure of the 

diagonal of the scanned rectangular area. 

As shown in Table 2, common imager formats today are in inches: 2/3, 1/2, 1/3, 1/4, 1/6, and 

1/8 inch. The inch measurement is a carryover from tube image cameras and relates to tube 

diameter, not the actual measurement of the diagonal of the imager. Early analog video 

cameras had 1-inch-diameter tube-type imagers. A 1-inch tube-type imager had a 16-millimeter 

(mm) (0.63-inch) active area. When solid-state imagers were manufactured, the sizing 

convention continued, so that an imager with a 16-mm diameter and 12.8-mm horizontal 

dimension was referred to as a 1-inch imager. Subsequently, as smaller imagers were 

produced, the imager format size relationship continued with the existing solid-state sizing 

convention. 

The ratio of the imager width to height is called the “aspect ratio.” Standard video camera 

imagers have a 4:3 horizontal to vertical size (aspect) ratio that represents two sides of a 3-4-5 

triangle. The vertical dimension is 0.75 times the horizontal dimension and the diagonal is 1.25 

times the horizontal dimension. Imagers for high-definition television (HDTV) cameras have a 

16:9 horizontal to vertical size ratio where the vertical dimension is 0.5625 times the horizontal 

dimension and the diagonal is 1.1475 times the horizontal dimension. 

Table 2 Imager Formats, Converting Inches to Millimeters 

Stated Format Active Area Imager Size (H x W)

1 inch = 16 mm diameter = 9.6 mm x 12.8 mm 

2/3 inch = 11 mm diameter = 6.6 mm x 8.8 mm 

1/2 inch = 8 mm diameter = 4.8 mm x 6.4 mm 

1/3 inch = 6 mm diameter = 3.6 mm x 4.8 mm 

1/4 inch = 4 mm diameter = 2.4 mm x 3.2 mm 

1/6 inch = 3 mm diameter = 1.8 mm x 2.4 mm 

1/8 inch = 2 mm diameter = 1.2 mm x 1.6 mm 

6.2.3.2 Scene Contrast 

Video image contrast relates to the difference between the white and black video signal levels in 

a picture image. High contrast indicates a large difference between the white and black levels, 

while low contrast indicates a small difference between the white and black levels. A 

low-contrast video image appears as shades of the same color hue. Figure 67 shows images of 

high- and low-contrast video scenes. 
 6-13 

 

Figure 67: Images of high-contrast (left) and low-contrast (right) scenes. 

6.2.3.3 Sensitivity 

The sensitivity of a video camera can be defined as the minimum amount of illumination 

required to produce a specified output signal. The following factors are involved in producing a 

video signal: 

 Illumination level of the scene 

 Color spectral distribution of the illuminating source 

 Object reflectance 

 Total scene reflectance 

 Camera lens aperture 

 Camera lens transmittance 

 Spectral response of the camera imager 

 Video amplifier gain, bandwidth, and signal-to-noise ratio 

 Electronic processing circuitry 

Camera sensitivity may also be expressed as scene illumination or the level of imager 

illumination that will produce a minimally acceptable video image. Normally, camera sensitivity 

is stated in units of lux or foot-candles. For practical purposes, experts in the field indicate 

camera sensitivity to be the illumination level that produces a 60-percent reduction in camera 

output. While usable camera video can be observed at levels below a 40-percent signal level, 

further reduction beyond 40 percent increases the amount of video signal noise and picture 

graininess. Below (Figure 68) is an excerpt from a camera specification page showing a 

sensitivity specification. 
 6-14 

Sensitivity 

Full Spectrum With IR Filter

Full Video, No AGC 0.039 fc (0.39 lux) 0.15 fc (1.5 lux)

80% Video, AGC On 0.001 fc (0.01 lux) 0.006 fc (0.06 lux)

30% Video, AGC On 0.0002 fc (0.002 lux) 0.0009 fc (0.009 lux) 

Figure 68: Camera sensitivity at light level. 

6.2.3.4 Signal-to-Noise Ratio 

Camera signal-to-noise ratio (SNR) is the strength of video signal above the electronic noise 

level created by the camera’s electronic signal processing circuits. SNR is expressed in 

decibels (dB). The higher the SNR, the better the rating. With low SNR, the picture can appear 

grainy or snowy and sparkles of color may be noticeable. Noisy video produces poor-quality 

pictures. A good camera SNR is 50 dB or higher. 

6.2.3.5 Automatic Gain Control 

Automatic gain control is an electronic circuit in the camera that maintains a preset video output 

signal by increasing electronic amplification of the video signal for low illumination scene 

conditions. A primary method to control the amount of light reaching the camera’s imager is the 

motor-operated automatic iris lens system. The camera’s output video signal amplitude is 

monitored either externally by a circuit in the lens assembly or internally within the camera, and 

an iris-control drive signal is created to maintain the amplitude at some predetermined output 

level. As the video level decreases (meaning that there is not enough illumination reaching the 

camera’s imager), the auto-iris lens is driven to increase the size of the aperture. At some point, 

however, the iris is driven fully open, and further decreases in light level result in a reduced 

amplitude video signal. At this point, the electronic amplification is increased. As the light level 

is reduced even further, the improvement caused by electronic signal amplification is exhausted, 

and a very grainy picture is presented. To prevent grainy pictures, some cameras have a cutoff 

circuit that causes the camera to produce no output when picture graininess exceeds a certain 

threshold. 

6.2.4 Characteristics and Applications for Cameras 

Several camera characteristics enhance a camera’s ability to provide reliable assessment 

images over varying environmental conditions, as listed below: 

 High sensitivity can provide the brightest and highest contrast video image under widely 

varying lighting conditions. 

 Automatic gain control, auto-iris control, or auto-shutter control circuits maintain video 

image quality over a range of day and night lighting conditions. These features maintain 

good picture quality while bright lights such as vehicle headlights are in the scene’s field 

of view. The imager’s persistence is short enough to preclude image smearing during 

movement, and the image does not have a washout streak above and below a bright 

light in the camera’s field of view. 

 The camera has a history of reliability, durability, and resistance to environmental 

weather effects. 
 6-15 

6.2.4.1 Exterior Cameras 

Exterior cameras should be mounted on stable towers and mounts so that motion or movement 

in the wind is avoided. A wire frame tri-pole tower (instead of a wooden pole) is unaffected by 

varying weather conditions. 

Exterior cameras should be mounted at heights of 7.6 to 9.1 meters (25 to 30 feet) above the 

assessment area surface. The cameras should be tilted down to view the entire assessment 

area. On flat perimeter surfaces, camera downward tilting on the order of 2 to 5 degrees is 

recommended. With the cameras tilted down, the horizon is not in the camera’s field of view, 

and glare at sunrise and sunset is reduced. In addition, particularly if the camera’s enclosure is 

covered with a sunshield, snow and ice impingement on the camera enclosure’s front cover 

glass is reduced. Exterior lighting luminaires should be at least 3 meters (10 feet) higher than 

the cameras. For example, if the cameras are mounted on top of 9.1 meter (30 foot) towers, 

lighting luminaires should be affixed to poles that place them at least 12.2 meters (40 feet) 

above the ground. All camera systems, associated power supplies, and connections should be 

protected from unauthorized external manipulation such as tampering. 

6.2.4.2 Camera Enclosures 

Exterior cameras require environmental enclosures to protect cameras from outdoor 

temperature extremes, dust, dirt, humidity, wind, rain, and snow. The enclosures must be large 

enough to contain the camera, lens assembly, power supply, and, possibly, camera 

communication modules. Two types of environmental enclosures are described below: 

 An integral environmental enclosure is normally cylindrical in shape and has an O-ring 

sealed cover glass and rear cover. The enclosure is of rigid construction and can be 

pressurized with dry nitrogen and has integral front cover glass heaters. A sunshade 

protects the camera enclosure from high summer temperatures by shading the 

enclosure and providing a shade to cover the front cover glass of the enclosure. 

 A sheet metal, formed metal, or fiberglass enclosure permits camera access through a 

clamshell-type cover (like the hood on a car). The cover is either hinged or removable. 

These enclosures cannot be pressurized. The large sealing surface and enclosure 

manufacturing techniques normally do not provide for a dust-tight seal. The primary 

advantage of the clamshell-type enclosure is for ease of accessibility for camera/lens 

replacement and for ease of lens focus adjustment. 

Accessories for exterior enclosures include heaters, insulation material, fans, defrosters, and 

front cover glass washers and wipers. Washers and wipers tend to be high-maintenance items 

with the need for frequent washer solution and wiper blade replacement. 

6.2.4.3 Pan-Tilt-Zoom Cameras 

In addition to fixed alarm-assessment cameras, PTZ cameras have been installed in facilities as 

an added capability for tactical surveillance. These cameras require controller electronics and 

an operator joystick control to facilitate camera movements. While PTZ cameras are not 

recommended for alarm assessment, they are effective for monitoring temporary operations 

such as a construction crew working near a fence line. They can also be used as a means to 

facilitate a compensatory measure in the event of an assessment camera outage. A PTZ 
 6-16 

camera can be positioned to view the area covered by a defective fixed camera and joystick 

control locked-out for that camera. 

6.2.5 Additional Considerations for Cameras 

Camera capabilities can be inhibited by positional errors in camera placement, mismatches in 

expected and actual resolution, overt or covert tampering, environmental conditions, and overall 

system response time. The relationship between expected camera resolution and actual need 

is described in the resolution section above. For example, if target identification is the security 

objective and the chosen camera resolution can provide only target detection, then the camera 

and lens installed at that location are inappropriate for the application. 

Covert video signal tampering can be accomplished in analog camera systems by tapping into 

video transmission cables and inserting a recorded scene or by switching video feeds to show 

video from the wrong zone. Overt tampering includes the following: 

 Using a bright light or laser to blind the camera 

 Covering the camera 

 Shooting the camera lens or enclosure cover glass with a paint gun 

 Cutting video transmission cables 

 Destroying the camera to make it totally nonfunctional 

Placing a camera in an unprotected area could lead to undetected camera tampering and attack 

on the camera’s video transmission infrastructure. Further, the camera tower could also be 

used to enable egress across a perimeter, which would circumvent detection by ground-based 

sensors. 

Changing environmental conditions such as rain, fog, or blowing snow can be the source of 

video assessment system weaknesses. These conditions can cause the loss of usable images, 

necessitating the implementation of contingency plans to provide an alternate form of alarm 

assessment, such as dispatching patrols to the area. 

When designing an intrusion detection system, the sensored areas and the video assessment of 

those areas should be considered together so that the entire detection area can be assessed. 

The design should ensure that there are no locations in the sensor detection area where an 

intruder could hide to avoid camera assessment. Cameras, mounts, and towers are placed so 

that they do not interfere with or compromise sensor performance. Camera towers should not 

be placed so close to the sensor detection area or volume as to create nuisance alarms, 

decrease sensor sensitivity, or be used by the intruder as a climbing aid to bridge a sensor’s 

detection zone. In multiple sensor configurations, the assessment camera should be able to 

view the combined sensored areas and volumes, as well as all of the hardware such as junction 

boxes or field data panels associated with the sensor. Sensor hardware should not be large 

enough to provide a convenient hiding place for intruders in video assessment areas. 

Wooden poles are not recommended because they will dry out and twist over time. To 

compensate for twisting action of the wood, cameras must be repositioned from time to time to 

maintain the proper view of the area to be assessed. 
 6-17 

Video assessment in shadows surrounded by bright sunlight creates significant problems 

because of the high scene dynamic range in brightness levels. In these circumstances, a 

compromise must be made to select the area of prime interest and to ignore the unresolved 

areas. 

If exterior cameras are positioned so that the horizon is in the camera’s field of view, it is 

possible (particularly for east- and west-facing cameras) for the rising or setting sun to be in the 

camera’s field of view, blinding the camera and allowing an adversary to enter the perimeter 

without being adequately assessed. Similarly, interior cameras with lights in the camera’s field 

of view can experience a glare or bright spots that will wash out usable images. In addition, a 

camera focused under one level of light and operated under a different light level or with a 

different lens mount or format will result in improper focus. Exterior cameras should be focused 

with the iris fully open at dusk to obtain optimum focus through the entire depth of field. 

Incorrect camera placement or lens selection can result in a horizontal field of view that is too 

narrow for the near field or not sufficient to see an individual or other target at the end of the 

assessment zone. 

Outdoor cameras should be installed so that no light sources are in the camera’s field of view. 

Direct light can cause image “blooming” or allow the auto-iris lens to close to reduce the amount 

of light allowed through the lens. Possible light sources include perimeter lighting, sky, exterior 

lighting on buildings, car headlights, and shiny objects that reflect light. Cameras should never 

be aimed so that the horizon and sky are in the camera’s field of view. Because a camera is a 

light-averaging device, images of the ground surface (particularly at low sun angles such as 

sunrise and sunset) tend to be darker and therefore harder to assess. Considerable care must 

be taken because camera blinding from unexpected light sources is difficult to predict before 

installation and is one of the most frequent problems encountered after equipment is installed. 

Illumination sources in a camera’s field of view may have to be shielded or reoriented to prevent 

the creation of a bright spot in the camera’s field of view. Perimeter isolation zones adjacent to 

a roadway can also be problematic. Reflections from vehicle headlights and tail lights from a 

roadway surface can affect alarm assessment capability. 

PTZ cameras should not be used for alarm assessment because of timing, reliability, and 

operational issues. PTZ cameras may compromise effective, timely alarm assessment. Use of 

PTZ cameras presents a high likelihood that they will be pointed at the wrong location or be 

zoomed so that part of the area to be assessed is not in the camera’s field of view. Only fixed 

cameras with fixed or manually adjustable zoom lenses should be used for alarm assessment. 

This provides pre- and post-alarm video of the entire assessed zone. PTZ cameras should be 

used only for tactical surveillance as an added feature to augment alarm assessment cameras 

or for backup in the event of primary camera failure. 

6.2.6 Criteria for Cameras 

The following considerations in camera selection are listed in order of priority: 

(1) The main consideration in camera selection is the sensitivity required for a full video 

output signal for the lighting environment in the area to be assessed. To meet the 

desired or required performance capabilities, the sensitivity must match the lighting 

design goals, regardless of the imager. 
 6-18 

(2) The resolution of the imager is next in importance because it will determine the 

number of cameras required for a given straight-line perimeter section. The greater the 

resolution, the greater the spacing between cameras can be. The object resolution 

required should be determined before the camera is selected, but in practice, the 

desired object resolution may be slightly modified when the possible camera choices are 

limited. 

(3) Camera format is an important consideration in the camera selection process. The 

requirements of nonstandard-sized focal length lenses should be carefully considered 

and evaluated before choosing a format. 

(4) During the selection process, camera evaluation should consider the nighttime lighting 

environment expected at the site. Manufacturers’ literature should not be the only 

basis for selecting a camera. The manufacturers’ specifications or test conditions may 

not match the environment at a particular facility. 

(5) Other considerations in the selection process should include the difficulty in 

performing maintenance, the packaging of the camera for the intended 

environment, the manufacturer’s maintenance support, and the documentation 

supporting the equipment. Documentation should include operating, adjustment and 

maintenance procedures, theory of operation, block diagrams, schematics, and 

replacement parts lists. Serious consideration should be given to eliminating any 

manufacturer’s product that does not include this documentation. 

Significant factors that affect the system performance of exterior location video assessment 

include the following: 

 Perimeter layout 

 Lighting layout 

 Weather effects (fog, heavy snow, etc.) 

 Surface conditions (flat with no hills for hiding, evenness of scene reflectiveness, rain, 

drainage) 

6.2.7 Testing Cameras 

Section 6.5 “Video Assessment System Testing” within this document contains testing 

information that should be approached from a systems point of view. This testing section 

addresses several kinds of testing, including acceptance, operational, and performance testing, 

integrating cameras, DVRs, lighting, and system elements. 

6.3 Digital Video Recorders

6.3.1 Principles of Operation 

Over the past 10 years, DVRs have almost totally replaced video cassette recorders (VCRs) for 

use in security video assessment applications and have significantly improved the process and 
 6-19 

quality of that video. DVRs record video onto arrays of hard drives and so do not require the 

changing or rewinding of tapes. The most typical DVRs on the market today, depending on the 

features purchased, can do the following: 

 Record the images obtained from 1 to 16 cameras simultaneously 

 Be set to record only when motion occurs in the camera scene, thus saving storage 

space 

 Instantaneously access recorded video from a particular time period 

 Store huge amounts of recorded video for weeks or even months 

 Adjust the number of frames per second of video to store from each camera, as well as 

the resolution of that stored image 

Modern DVRs are computer-based devices and can be controlled by an interactive system with 

the sensor alarm monitoring portion of a security system. Upon sensor alarm notification, the 

DVR can be directed to play back pre- and post-alarm video from the camera assessing the 

area covered by the alarming sensor. 

Video image recording is a process using a personal computer (PC) to capture a video stream 

and store that video information to a network of computer hard drive memories. It is then 

possible to play back video streams from the hard drive for operator display. The components 

of a video image recording system are a PC with video recording card, video recording software 

for managing the storage and playback of the video images, and a computer monitor for 

displaying the video images. The video management software allows the computer to display 

incoming video on a monitor, record images, store incoming images to the hard drive, and play 

back stored images from several cameras on the monitor simultaneously. 

Incoming camera analog video signals are separated into their main components (luminance 

and chrominance), then converted to a digital format so that they can be stored on a computer 

hard drive. Luminance contains the black and white portion of the video signal, and 

chrominance contains the color portion. Digital filters are applied to each pixel (picture 

element) of the video image to ensure that every single pixel of video image is represented in 

digital format with the highest accuracy. Once the analog video signal has been converted to a 

digital signal, a certain amount of signal noise (white noise and other visual imperfections) 

results from the conversion process that needs to be removed before the next step of video 

processing, called compression. Noise reduction software algorithms clean up the digital video 

information to provide better video quality, improve video encoder compression efficiency, and 

improve video content of the stored images. 

To maximize the amount of video images that can be stored on a particular DVR system, video

compression uses a coder decoder (codec) to compress video content into a reduced size 

format using an encoding scheme to fit efficiently onto a hard drive memory. For example, 

without compression, a 2-hour movie would need to be stored on 30 DVDs rather than just one. 

Compression encoders include Motion Picture Experts Group (MPEG format), Joint 

Photographic Experts Group (JPEG format), Motion JPEG (M-JPEG format), H.2.64, and 

Wavelet. The H.2.64 compression has its roots in coding for videoconferencing and video 

telephony, as well as streaming broadcast, file download, and media storage and playback. 

Wavelet algorithms for video compression originated in Europe. DVR manufacturers have 
 6-20 

either adopted a compression scheme derived from one of the types described above or have 

created their own proprietary compression algorithm by combining portions of standard 

compression codecs. DVR manufacturers more often use MPEG encoder compression 

because of the efficiency of video compression and the quality of the reconstructed playback 

image. Compression encoders analyze the video and decide which pieces of video information 

can be eliminated because they do not contain important visual content or contain redundant 

information, such as an image background that is all the same color. 

Once the video is stored in computer hard drive memory, retrieving images for playback 

requires that the video images be processed by several software algorithms before display on a 

computer monitor. The stored images must be uncompressed and reformatted to produce a 

series of pictures that, taken in timed sequence, replicates the initial analog images from which 

the stored video was obtained. Reconstituted images can contain rough or harsh edges, so a 

smoothing algorithm is applied to the edges of objects to make them appear more natural. 

Finally, a scaling algorithm is applied to adjust the picture to the size of the screen and clean up 

the edges of the picture. Scaling is also applied when image size is adjusted to display images 

simultaneously from several cameras on the same monitor screen or change the shape of the 

image displayed from its initial image size. 

The standard frame rate for analog cameras operating to Electronics Industry Association 

standards is 30 frames per second. The maximum DVR video recording rate is specified in 

frames per second (FPS). Most DVRs can record video at rates of at least 30 FPS. However, 

many cannot record simultaneously at that frame rate on all channels (each channel serves one 

camera). The maximum recording rate in FPS must be divided among all the cameras served 

by a DVR unit, though this does not have to be an equal number of frames for each camera. If 

a 16-channel DVR has a maximum recording rate of 240 FPS, on average, if all channels are 

being recorded at the same frame rate, a maximum of 15 frames per channel can be allocated 

per channel. Because DVRs are computer based, the number of frames to be captured from 

each camera can be customized based on the camera, the time of day, or the type of received 

alarm that initiates the recording. 

6.3.2 Types of Digital Video Recorders Available 

DVR technology is evolving at the same rate as general computer technology. Capabilities and 

features of commercial DVR systems change radically every 12 to 18 months. 

Some DVRs can control as many as 32 to 64 cameras each, though this feature is not 

necessarily advantageous if the system goes down; multiple DVR systems controlling only 

16 cameras each may be preferable, as a significant number of a facility’s cameras will not be 

rendered unavailable if one system becomes unavailable. 

The number of video frames a particular DVR can record at any one time is also increasing 

dramatically. Minimum systems will record 30 FPS; newer systems can record as many as 

240 or more FPS. 

6.3.3 Minimum Configurations and Installation and Setup Requirements for Digital Video 

Recorders 

A DVR should contain a reasonably fast microprocessor, which at a minimum, should possess 

the following characteristics: 
 6-21 

 At least 1 gigahertz clock speed or higher 

 At least 256 megabytes (MB) of RAM 

 At least a 5,400-rpm, 300-gigabyte hard drive 

 A video recording card with at least 64 MB of onboard memory 

 Special software dedicated to simultaneously processing multiple streams of video and 

responding to control commands from a security alarm control and display system 

The system should have at least a 17-inch monitor (preferably larger where possible) with at 

least a 1,024  768 pixel 32-bit color display. A 10/100 MB network connection is required for 

streaming digital video from the video image recording computer to the operator’s console. 

Existing analog cameras can connect directly to DVR analog inputs. Digital cameras can 

connect to recorders called network video recorders using Ethernet networks. A DVR can be 

implemented as a group of stand-alone boxes, or it can be integrated into a desktop 

computer-type configuration. 

Most DVR systems are considered to be user friendly, employing simple VCR-type control 

commands such as play, stop, fast-forward search, fast-reverse search, and enhanced digital 

control commands to play back-tabbed video associated with a specific alarm event. Because 

the DVR is computer based, many setup and control parameters can be customized for each 

application. 

6.3.3.1 Raw Camera Images versus Recorded Images 

To determine if the configuration of a DVR (or even the DVR itself) is adequate for purposes of 

assessment video playback, the output of the raw camera image should be compared to the 

same image played back from the DVR. Viewing the output of a DVR while recording is taking 

place is not a definitive means for making a comparison. Most DVRs have a loop-through 

output that takes the incoming camera input video and connects it to the video output connector. 

What is recorded and subsequently (and instantaneously) retrieved from the hard disks may 

have a significantly reduced resolution from the raw camera image. Therefore, it is important 

that when conducting resolution tests, actual playback images from the hard disk be compared 

to the raw camera images. 

6.3.3.2 Digital Transport 

A DVR can be used to copy video clips and images to portable memory devices for transport 

from the alarm station and for evidentiary purposes. Networked DVRs can be set up to send an 

e-mail with alarm video to response force personnel or offsite personnel for immediate 

response. 

6.3.3.3 Memory Management 

A DVR’s memory management can be configured to overwrite previously saved video when the 

maximum memory storage limit is reached or when the oldest video has exceeded its maximum 

storage time limit. DVR output display configurations allow for single or multiple camera images 
 6-22 

to be viewed as separate windows or panes on digital display monitors. Monitor views can be 

configured to simultaneously display live and recorded alarm video. 

6.3.3.4 Video Motion Detection 

Video motion detection (VMD), a feature available in most DVRs, allows the DVR to 

automatically store video when a movement within a camera’s scene is detected. It can be set 

up to allow secure access to recordings using the Internet and secure communications and 

access controls. (See Figure 69.) 

Figure 69: Video motion detection image showing intruder tracking. 

The video storage capacity of a DVR system is determined by the following factors:

 Amount of hard disk drive storage space 

 Number of simultaneous video channels being recorded (i.e., the number of cameras) 

 Number of frames captured per second (frame rate) for each camera 

 Video image resolution (pixels per frame) 

 Quality of video recorded (compression) 

The file size of recorded images can be controlled by reducing the captured resolution. DVR 

resolution is represented as a pixel count or in a video format term called “common intermediate 

format” (CIF). CIF is a standard video format used to define resolution in terms of pixel count. 

Table 3 shows format in terms of CIF, pixel resolution of that format, and the size of an 

uncompressed video image with that format. 
 6-23 

Table 3: Image Sizes for Common Intermediate Format Image Sizes

Format Resolution 

(Pixels) Uncompressed Image Size (kB)

CIF 352  288 250 

QCIF 176  144 63 

4CIF 704  576 1,000 

16CIF 1408  1152 4,000 

The size of the video files stored on the hard drives can be reduced by increasing the degree to 

which each captured image is compressed. A good camera may provide a high-resolution 

image, but the captured image may be compressed to save storage space. To view a recorded, 

compressed image, the image is decompressed, but when viewing the decompressed image, 

image detail can suffer. Overall image quality is a function of camera resolution, captured 

image resolution, and the amount of compression applied to the original digital image. 

6.3.4 Testing Digital Video Recorders 

The last portions of this section contain testing information that should be approached from a 

systems point of view. The testing section addresses several kinds of testing, including 

acceptance, operational and performance testing, integrating cameras, DVRs, lighting, and 

system elements. 

6.3.5 Digital Video Recorder Maintenance 

Maintenance for a DVR system is minimal. The manufacturer’s suggested maintenance 

schedule should be followed. 

6.4 Lighting

6.4.1 Lighting for Video Assessment 

6.4.1.1 Principles of Operation 

Lighting for alarm assessment allows security personnel to maintain visual assessment 

capability during darkness. When security lighting provisions are less than optimal, additional 

security posts, patrols, night-vision devices, or other provisions are necessary for acceptable 

alarm assessment. 

Security lighting should be used in vital areas and along perimeter fences when the situation 

dictates that the area or fence must be under continuous or periodic observation during 

nighttime hours. 

Lighting when properly used in conjunction with video cameras may reduce the number of 

security personnel needed for alarm assessment. It may also enhance the personal protection 
 6-24 

of security personnel by reducing the possibilities of concealment and attack from a determined 

intruder. 

Security lighting is desirable for those sensitive areas or structures within and at the perimeter 

that are under constant video observation. Such areas or structures include perimeter isolation 

zones, vital buildings, storage areas, and vulnerable control points of communication, power 

supply, and utility infrastructure systems. In interior areas where night operations are 

conducted, adequate lighting facilitates the detection of unauthorized persons approaching or 

attempting malicious acts within the area. Security lighting also has considerable value as a 

deterrent to intruders and may make the job of the adversary more difficult. Lighting is an 

essential element of an integrated physical security program. 

A secure emergency power source (such as an uninterruptible power supply (UPS)) and power 

distribution system for the facility should be installed to provide power source redundancy for 

critical security lighting, as well as for security detection and assessment, control, and 

monitoring equipment. If primary power is temporarily lost as the result of power system 

outages or hostile activity, an emergency power supply enables critical security equipment (e.g. 

detection, assessment, illumination, control, and monitoring assets) to remain operable thus 

maintaining the integrity of the physical protection system employed at the facility. Emergency 

power sources should be available immediately without functional interruption for critical 

electrical loads and should be secured against direct and indirect attack as well as sabotage. 

Perimeter lighting needs should be based on the threat, site conditions along the perimeter, 

video assessment capabilities, and available security personnel. Security lighting should be 

designed and operated to facilitate the detection of intruders approaching or attempting to gain 

entry into protected areas and to discourage unauthorized entry. 

An effective lighting design is of paramount importance to the proper functioning of alarm 

assessment systems. Just as humans need good lighting to see, most security video cameras 

require appropriate lighting to allow for efficient assessment of the area when natural light is not 

adequate or available. 

Intuitively, it would seem that an organization could order poles and an exterior luminaire to 

install at the top of each pole, run power lines, and then set the poles and light fixtures evenly 

spaced along the areas to be assessed. It might also seem that brighter lamps would require 

fewer poles and luminaires. However, that concept is not the optimal approach from a camera 

assessment perspective. To compare how lighting affects assessment, note the differences in 

the evenness of illumination between Figure 70 and Figure 71. Figure 70 has one very bright 

spot that affects camera performance and dark spots where an adversary might hide. In the 

event of an alarm condition, the scene depicted in Figure 71 would allow for a more efficient 

video assessment to determine the cause of the alarm so that security personnel can be 

appropriately dispatched. 
 6-25 

Figure 70: Example of lighting with hot spots, dark areas, and dirt ground cover. 

Figure 71: Assessment visibility improved with even lighting and a regular ground surface material. 

If a facility is using thermal imaging cameras as the means for providing alarm assessment at 

night, illumination in the specific areas covered by these cameras is not as critical; however, it 

may still be required to provide a means for the security force to identify and engage potential 

adversaries using a force continuum. If the potential exists for the security force to use deadly 

force for the protection of the facility, illumination is a critical component that enables security 

force members to properly identify and accurately engage the adversarial force after detection 

and assessment are complete. 

6.4.2 Installation Criteria 

Security lighting usually requires less illumination than normal task lighting, except for personnel 

identification and vehicle inspection at an entry control point. Each area of a facility presents its 

own unique set of considerations based on physical layout, security requirements, terrain, and 

environmental and climatic conditions. Information that is available from lighting equipment 
 6-26 

manufacturers and vendors of lighting analysis software to assist in designing a lighting system 

includes the following: 

 Descriptions, characteristics, and specifications of luminaires and lamps 

 Luminaire lighting patterns 

 Installation layouts showing height and spacing of luminaires to achieve light levels 

Desired 

 Software to produce computer-generated plots of illumination levels and lighting 

uniformity in a particular zone and summary statistics of the illumination profile

 Average illumination level 

 Light-to-dar k ratio 

 Maximum and minimum illumination 

In planning a security lighting system, the site designer should consider the following: 

 The cost of replacing lamps and cleaning fixtures, as well as the cost of providing the 

required equipment (such as ladders and bucket trucks) to perform this maintenance 

 Provision of automatic transfer or manual-override capability during a loss of primary 

power 

 Photoelectric controls for automatic control of lights during nighttime hours 

 Effects of local weather conditions on lighting systems 

 Fluctuating or erratic voltages in the primary power source 

 Grounding requirements 

 Provisions for rapid lamp replacement and luminaire cleaning 

 Special lighting requirements for critical areas (such as protected area perimeters), 

lighting provided with the means to remain operable without interruption during the loss 

of primary power. Any amount of time without adequate lighting in a critical area may be 

unacceptable. Therefore, these areas generally have emergency power (such as 

uninterrupted power supplies consisting of batteries and diesel engine generators) in 

case of primary power loss. 

 Continuous operation of security lighting systems during hours of darkness 

 Security lighting system configured so that the failure of one or more lights will not affect 

the operation of the remaining lights 

 Restrike time (the time required before a light will function properly after a brief power 

interruption) 

 Color spectrum of bulbs 

6.4.3 Principles of Security Lighting 

Security lighting enables security personnel to observe activities using alarm assessment and 

surveillance cameras around or inside a facility while minimizing their physical presence 

throughout the facility. Having adequate illumination levels at all approaches to a facility does 
 6-27 

not necessarily discourage unauthorized entry. However, adequate lighting improves the ability 

of security personnel to visually assess intrusion alarms with the use of video cameras and 

intervene in the event of an unauthorized access attempt. Lighting is implemented with other 

security measures, such as intrusion detection sensors, video assessment equipment, and 

alarm control and display systems as part of an integrated facility security system. 

Optimum security lighting is achieved by adequate, even light in perimeter isolation zones. 

Additionally, the use of deterrent lighting (i.e., glaring lights directed away from the fenced 

perimeter) can augment security perimeter lighting as a psychological deterrent to intruder 

ingress. In addition to seeing long distances, security personnel must be able to see low 

contrasts, such as indistinct outlines of silhouettes and must be able to detect an intruder who 

may be exposed to view for only a few seconds. Higher levels of illumination, such as that 

provided by deterrent lighting systems, if properly implemented, can improve these assessment 

abilities. 

Contrast between an intruder and the background should be an important consideration when 

planning for security lighting. With predominantly dark surfaces, more light is needed to 

produce the reflective brightness required for camera assessment than would be necessary if 

neutral gray backgrounds and ground cover are used. When the same amount of light falls on 

an object and its background, the observer must depend on the contrast of light reflected from 

each to determine intruder location. The ability to differentiate between background and objects 

of interest when contrast is poor can be improved significantly by adjusting the illumination level 

or the lighting location. (See Figure 72.) 

 

Figure 72: At left, poor contrast created by outdoor lighting; at right, better contrast created by outdoor 

lighting. 

The observer primarily sees an outline or a silhouette when the intruder is darker than the 

background. Using light-color finishes on the lower parts of buildings and structures may 

expose an intruder who depends on dark clothing and darkening the face and hands. Placing 

stripes on walls has also been used effectively as patterns that can provide recognizable breaks 

in outlines or silhouettes. 

Security lighting should be practical and effective. To be effective, it must discourage or deter 

intruder access attempts and, if access is attempted, it should facilitate detection and 

assessment. It is important that security lighting be designed to provide sufficient illumination so 

that security personnel can effectively observe an intruder with the naked eye but not be so 

bright as to create a glare that may temporarily blind the security personnel. 
 6-28 

The eyes of security force response teams dispatched from building interior locations will not be 

night-adapted before they respond to an intrusion alarm at an exterior location where light levels 

are below 0.5 f-c (5 lux). Full sensitivity change (adapting to a significantly lower light level) may 

take up to 30 minutes, making proper illumination in exterior areas critical to the effectiveness of 

the responding security force. 

6.4.4 Types of Lighting 

The type of lighting system used depends on the installation’s overall security requirements. 

Four types of lighting approaches can be used for security lighting systems: continuous, 

standby, movable (portable), and emergency. 

6.4.4.1 Continuous Lighting 

Continuous lighting is the most common type of security lighting used. As shown in Figure 73, it 

consists of a series of fixed lights arranged to continuously illuminate a given area during 

darkness with overlapping cones of light. Two primary methods of using continuous lighting are 

controlled projection lighting and deterrent glare projection lighting. 

Figure 73: An example of a perimeter with controlled lighting. 

6.4.4.1.1 Controlled Lighting

Controlled lighting is optimum when the limits of the width of the lighted strip are directed to 

illuminate the inside of a perimeter isolation zone with minimal illumination of the areas inside 

the perimeter. Having too much illumination on the protected side of the perimeter may 

illuminate or silhouette security personnel, giving the intruder an unnecessary visual advantage. 

6.4.4.1.2 Deterrent Glare Projection Lighting

Deterrent glare projection security lighting (such as spotlights) is used when the glare of lights 

directed across the surrounding territory will not interfere with adjacent operations or be 
 6-29 

politically unacceptable to neighbors. These types of lights are a strong deterrent to a potential 

intruder because they make it difficult for a would-be intruder to see inside the area. Security 

personnel are protected by being in comparative darkness and being able to observe intruders 

who are at a distance outside the perimeter. 

6.4.4.2 Standby Lighting 

Standby lighting has a layout similar to continuous lighting. However, the luminaires are not 

continuously lit during nighttime hours but are either automatically or manually initiated when 

suspicious activity is detected or suspected by security personnel or the intrusion sensor 

system. 

6.4.4.3 Movable Lighting 

Movable lighting consists of manually operated, movable integrated luminaire and generator 

assemblies that may be operated during hours of darkness or as needed. This type of system 

is normally used to supplement continuous or standby lighting. 

6.4.4.4 Emergency Lighting 

Emergency lighting is a system of lighting that may duplicate any or all of the above systems. 

Its use is limited to times of power failure or other emergencies that render the normal system 

inoperative. It depends on an alternative power source such as installed or portable generators 

or battery-powered UPS. 

6.4.5 Lighting Definitions 

Illuminance, defined as the intensity of illumination incident on a surface area, is stated in 

terms of “foot-candles” or “lux,” which are not equivalent measurements. One foot-candle (f-c) 

is defined as the intensity of illumination on a 1-square-foot surface from a 1-lumen source of 

light located 1 foot away. One lux is the international system of units (SI) standard unit (metric) 

for illuminance, defined as the illumination on a 1-square-meter surface from a 1-lumen source 

located 1 meter away. One f-c is equal to 10.76 lux. For ease of conversion, industry practice 

uses 10 as the conversion factor between unit systems (i.e., 1 f-c = 10 lux). 

Illumination is either natural or artificial. Natural illumination emanates from the sun, moon, and 

stars. Artificial illumination is manmade and comes from an illumination source such as a 

luminaire. 

Table 4 provides the approximate illumination levels for nine natural lighting conditions. As 

shown, the range of illumination from direct sunlight to starlight in an overcast sky spans about 9 

orders of magnitude. However, cameras do not have the ability to compensate for that range of 

natural illumination. Therefore, luminaires must be used to illuminate assessment areas during 

nighttime hours. This reduces the dynamic range of camera compensation for daytime and 

nighttime lighting conditions to only 4 orders of magnitude.
 6-30 

Table 4: Relative Illumination Levels under Various Lighting Conditions 

Direct Sunlight 3,200 to 13,000 f-c 

Full Daylight (not direct sun) 1,000 to 2,500 f-c 

Overcast 100 to 1,000 f-c 

Sunrise or Sunset (clear day) 20 to 60 f-c 

Twilight 0.1 to 10 f-c 

Full Moon (clear) 0.01 to 0.1 f-c 

Full Moon (overcast) 0.001 to 0.01 f-c 

Starlight (clear) 0.0001 to 0.001 f-c 

Starlight (overcast) 0.00001 to 0.0001 f-c 

A scene becomes visible when illumination is reflected from surfaces and objects within that 

scene. Reflectance, the percentage of light reflected from a scene, depends on the angle of 

the light incident on the surface of a scene and on the texture and composition of the reflecting 

surface. Reflectance is determined by measuring illumination with a light meter’s sensor facing 

down, divided by the illumination measurement with the light meter facing upward. (The 

measurement should be made such that neither the light meter nor the person making the 

measurements create a shadow on the sensor when face up or on the ground just below the 

light sensor when face down.) For natural illumination, the reflectance of various scenes is 

relatively independent of the angles of incidence and reflection. Table 5 lists some common 

surfaces and their approximate reflectance. 

Table 5: Typical Reflectance for Various Common Surfaces 

Surface Reflectance (%) 

Empty asphalt surface 7–10 

Sandy soil, wet 15–20 

Grass-covered area with trees 20–25 

Gray rounded river rock 25–35 

Red brick building 30–35 

Sandy soil, dry 30–35 

Unpainted concrete 35–40 

Smooth surface aluminum 60–65 

Snow-covered field 70–75 

To ensure that a sufficient amount of the nighttime illumination is reflected back to the camera 

and that sufficient scene contrast exists for intruder detection, the ground surface of the 

assessment area should have a nominal reflectance of 25 to 35 percent when dry. 

Illumination is typically measured using a light meter with the sensor face up at a specified 

distance above a horizontal ground plane. Normally, measurements are made at 6–12 inches 

above the ground. An area’s average illumination is determined by taking several 

measurements of illumination at equally spaced locations in an illuminated area or zone. For 

example, measurements are taken in straight lines at 10-foot intervals in both the lengthwise 

and widthwise directions within a perimeter isolation zone beginning at one fence line and 

ending at the opposite fence line. Several measurements can be taken within an area or zone 
 6-31 

covered by a number of lamps and then averaged together. These are measurements of 

“horizontal scene illumination,” or simply scene illumination. 

Average scene illumination is the average amount of light illuminating an assessment area. 

The average scene illumination must be high enough to achieve adequate alarm video 

assessment, as well as visual assessment by security personnel. Tests have shown that an 

average scene illumination of 1.0 f-c onto a ground cover surface with 25 to 35 percent 

reflectivity provides sufficient light for camera and security personnel assessment purposes in 

clear environments. 

The “evenness” (also referred to as “flatness”) of scene illumination enhances the ability to 

assess intruder location. The scene at left in Figure 74 has a light-to-dark ratio of approximately 

20-to-1 (20:1). The scene at right in Figure 74 has a light-to-dark ratio of approximately 4-to-1 

(4:1). Tests have shown that lighting designs with at least a 6-to-1 (6:1) light-to-dark ratio at the 

end of bulb life provide sufficient illumination evenness for assessment purposes. 

 

Figure 74: The scene at left has a high light-to-dark ratio of approximately 20:1, which is not considered 

sufficient. The scene at right has a low light-to-dark ratio of approximately 4:1, which maximizes the ability 

to assess an alarm. 

A scene light-to-dark ratio of 6:1 should be considered to be a maximum (i.e., the lightest part of 

the scene being examined should be no more than 6 times brighter than the darkest part of the 

scene). A design ratio of less than 4:1 is strongly suggested for exterior lighting. Historically, 

assessment lighting systems have been designed to produce a 4:1 light-to-dark ratio at 

installation to allow degradation to a 6:1 ratio as bulbs produce a lower lumen output during their 

service life. At least 75 percent of the camera’s field of view should have an even illumination 

that meets the minimum average illumination and light-to-dark ratio requirements. 

Using the lens iris control, exposure time, and electronic signal amplification, a camera 

averages the total scene brightness detected by the imager. As a result, there is a limit to the 

amount and intensity of bright areas and dark areas in the camera’s field of view for which the 

camera can compensate. This is known as the camera’s dynamic range. Bright spots in the 

camera’s field of view raise the average imager illumination level, causing the camera 

electronics to compensate by lowering the average video signal output. This tends to cause the 

darker portions of the image to become too dark and will negatively impact an operator’s ability 

to assess the scene. To mitigate camera dynamic range limitations, a maximum scene 

light-to-dark ratio should be specified and implemented in the lighting design. If the light-to-dark 
 6-32 

ratio is excessive, light areas will provide too much light, causing a saturation of details within 

those areas. Likewise, dark areas will not provide sufficient light for good resolution. 

Therefore, to maximize video assessment performance, the scene light-to-dark ratio should not 

exceed 6:1. This includes the entire area observed by the camera and not just the area of 

interest. To accomplish this, the lighting should extend beyond corners and fences to provide 

even illumination within 75 percent of the camera’s field of view. As discussed previously, the 

outdoor perimeter area should use ground cover materials that provide a 25 to 35-percent 

reflectance. 

6.4.6 Range of Scene Illumination Readings 

If a minimum average scene illumination of 1.0 f-c and a 4:1 scene light-to-dark ratio is 

recommended at installation, a maximum and minimum set of illumination readings at the scene 

can be estimated. Table 6 shows a relative range of minimum to maximum illumination 

readings for average illumination values of 1.0 to 3.0 f-c. For example, given a normal 

distribution of illumination readings, if an average scene illumination is calculated to be 1.0 f-c, 

the individual illumination readings are estimated to be in the range of 0.5 to 2.0 f-c. 

Table 6: Ranges for Average Illumination Values That Will Give 4:1 Light-to-Dark Ratios 

Average 

Illumination (f-c) 

Relative Range 

(f-c) 

1.00 0.5–2.0 

1.25 0.6–2.5 

1.50 0.8–3.0 

1.75 0.9–3.5 

2.00 1.0–4.0 

2.25 1.1–4.5 

2.50 1.3–5.0 

2.75 1.4–5.5 

3.00 1.5–6.0 

With an understanding of the relative levels of scene illumination produced by various sources 

and the amount of light reflected from typical scenes, the expected effectiveness of the camera 

portion of the video assessment system can then be determined. The next step is to 

understand the camera imaging system being used for alarm assessment. 

6.4.7 Assessment Sensitivity 

Lighting for video alarm assessment must consider the camera, video processing, and the 

display system that produces images for security personnel to view. Whether assessment is 

accomplished by security personnel or video cameras, lighting is required to facilitate 24-hour 

alarm assessment. 
 6-33 

Since cameras are the primary mode of alarm assessment, camera sensitivity and lens aperture 

are two critical factors that affect the amount of reflected scene illumination appearing at the 

camera’s imager. Camera sensitivity is defined as the amount of illumination required at the 

camera’s imager to produce a usable video image. This basic rule applies whether the camera 

is analog or digital. The following factors contribute to producing a usable video assessment 

image: 

 Illumination and the flatness of illumination present at the scene 

 Spectral distribution (color of light) of the illumination source 

 Total scene reflectance 

 Object reflectance 

 Camera lens transmittance 

 Camera lens aperture diameter (f-stop) 

 Spectral response of the camera imager (camera imager sensitivity to color of light) 

 Camera imager sensitivity to broad spectrum light 

 Camera automatic brightness control (gain and exposure time) 

Under low light conditions, most cameras automatically compensate for the lack of illumination 

by increasing some combination of both the exposure time and amplifier gain depending on the 

overall brightness level desired by the user. Cameras with auto-iris lenses compensate for 

changing scene light levels by opening or closing the lens iris. The mechanics of illumination 

level compensation for some digital cameras can be programmed. The sequence of iris control, 

shutter control, and amplifier gain can be prioritized as to the order in which they are used to 

control imager illumination. Using shutter control for low light compensation causes the shutter 

to be open for longer exposure times. Long exposure times will blur moving objects while 

higher amplifier gain on very low light signals will produce grainier images. Both of these 

outcomes are undesirable for purposes of alarm video assessment. For example, fast-moving 

objects start to become noticeably blurry at exposure times greater than 1/6 of a second. The 

level of noise or amount of graininess in the monitor’s video image that is acceptable depends 

on the application and the subjective opinion of the alarm station operator. Most digital cameras 

allow for limits to be placed on the maximum exposure time and gain so that one parameter can 

be favored over the other. Typically, some image blur can be tolerated, rather than picture 

graininess. 
 6-34 

An industry standard for specifying camera sensitivity has not been established. Camera 

manufacturers often state camera sensitivity using varying test conditions and camera 

parameter settings. Often, camera sensitivity is stated in terms of minimum illumination level at 

the camera’s imager to provide a usable picture. These camera specifications do not account 

for the illumination level degradation caused by the camera lens. While the amount of light 

needed at the camera’s imager to produce a usable picture is specified, the amount of light that 

needs to enter the lens to achieve that light level at the imager may be significantly higher. 

Also, illumination and scene conditions during which the camera’s sensitivity is determined may 

not necessarily be documented in the camera’s specifications. Along with minimum light level, it 

is important to have the following information: 

 Condition of output video—camera output and/or gain and exposure time 

 Lens transmissivity—the percentage of incident light appearing at the front of the lens 

that passes through on to the imager 

 Lens f-stop—the level of light reduction to the imager determined by the lens iris (or 

aperture) opening 

 Test scene reflectance—the percentage of incident light on a scene that is reflected 

back to its source 

In some cases, the parameters used to claim sensitivity may be unrealistically assumed to 

indicate a better performance than will be experienced in actual installations. For example, 

three of the favored parameters for specification enhancement are (1) higher scene reflectance 

than normally encountered, (2) unacceptably long exposure times, and (3) a large lens aperture 

(low f-stop). These parameters are usually determined with the camera viewing a static scene. 

If the need to effectively observe motion is factored into the specification process, the actual 

camera sensitivity experienced would most likely be less than (i.e., not as good as) that stated 

on manufacturers’ data sheets. 

To calculate whether the scene provides sufficient camera imager illumination for the camera 

chosen, the formula shown below may be used. To calculate the amount of illumination from 

the viewed scene incident on the camera imager, the scene illumination, scene reflectance, lens 

f-stop, and lens transmittance must be known. The formula below is a quick way to check if 

there will be sufficient illumination on the camera’s imager surface to provide an adequate video 

picture. It is highly recommended, however, that a camera be field tested for verification under 

expected lighting conditions before its deployment. 

Imager Illumination = Scene Illumination x Scene Reflectance x Lens Transmittance

 4 x (Lens f-stop)2

where: 

Imager illumination is in foot-candles or lux 

Scene illumination is in foot-candles or lux 

Lens f-stop from lens specification 

Scene reflectance is in percent 

Lens transmittance is in percent 
 6-35 

For example, given an illuminated area and camera lens with the parameters shown below: 

Scene Illumination = 1 f-c 

Scene Reflectance = 0.3 (30%) 

Lens Transmittance = 0.8 (80%) 

Lens Focal Length = 1.8 

Using the equation above: 

Imager Illumination = 1 x 0.3 x 0.8 = 0.019 f-c or 0.19 lux 

 4 x (1.8)2 

From the example calculation, if a camera selected for video assessment had a sensitivity of 

0.05 lux, it would have more than adequate sensitivity for the application if used to assess an 

area with the scene illumination and reflection specified and the lens f-stop and transmittance 

shown above. The scene provides 0.19 lux and the camera requires a minimum of 0.05 lux. 

Therefore, the scene provides 0.14 lux more than the minimum camera sensitivity. 

Since most lighting applications are associated with bulbs that produce visible light, errors can 

be made in estimating the light required if the camera imager spectrum is not considered. An 

example of this relates to the use of color cameras. Most color cameras render color by 

masking pixels on an otherwise monochrome imager with red, green, and blue filters. In a 

typical camera imager configuration, 25 percent are red, 25 percent are blue, and 50 percent 

are green. The light spectrum is therefore filtered before it reaches the photo sensor resulting in 

degradation to the imager’s overall pixel sensitivity when compared with monochrome cameras. 

Additionally, only 25 percent of the pixels in a color imager are sensitive to infrared light, as 

compared to 100 percent of the pixels in a black-and-white camera. A color camera’s imager 

also has a blue filter in front of it that will further reduce its infrared sensitivity. If a near-infrared 

energy source is used, a black-and-white camera provides a visible video image even if the 

near-infrared illumination was not visible to the human eye. 

6.4.8 Conceptual Lighting Layout 

To prevent cameras from looking directly into a light source, security lights need to be located 

above the camera and out of the camera’s field of view. It is usually recommended that security 

lights be no less than 3 vertical meters (10 vertical feet) above the camera’s position. (See 

Figure 75.) It is further recommended that a light source not be directly above the camera to 

mitigate the potential effects of dust- and fog-induced backscatter. However, the use of a 

sunshield that extends beyond the front cover glass of a camera enclosure like the brim of a cap 

can also minimize those effects. 
 6-36 

 

Figure 75: Recommended height differences between exterior lighting and cameras. 

6.4.8.1 Lighting Design 

Using the lighting guidelines discussed earlier, manufacturers and suppliers of chosen lighting 

equipment should be consulted to obtain luminaire and bulb illumination characteristics. Most 

major lighting suppliers and architectural engineering firms can model a proposed lighting 

system to determine and plot expected scene illumination levels. Maximum and minimum levels 

of illumination and light-to-dark ratio can also be determined. With access to such modeling 

software, several possible lighting configurations can be quickly evaluated. The inputs to the 

model normally include a file containing photometric data specific to a particular type of lamp 

(provided by the lamp manufacturer); luminaire light pattern (provided by the fixture 

manufacturer); and luminaire orientation, mounting height, and light pole spacing. A facility that 

is going to perform extensive lighting work should consider a lighting software program for inhouse use; this type of software is generally not expensive. Figure 76 illustrates an example of 

output from an illumination modeling software package. 
 6-37 

Figure 76: An example output from an illumination modeling software system. 

The computer-generated modeling software illumination output pattern shown in Figure 77 

provides data for a region of interest with expected illumination levels (i.e., numbers within the 

dashed lines expressed in f-c) and other pertinent statistics. Note that the area calculated can 

represent data for a particular perimeter isolation zone. 

The lighting design should be physically tested before installation in the final perimeter lighting 

configuration. This is accomplished by installing a minimum of five fixtures (for single-row 

installations) and actually measuring the illumination provided. Measurements should be made 

at 6 to 12 inches above ground level, taking measurements at 10-foot increments in the length 

and width dimensions. The brightest and darkest measurements should be identified, average 

illumination level calculated, and light-to-dark ratio calculated. Measurements should extend to 

distances where the light level is above 0.2 f-c. 
 6-38 

Light measurements are taken using meters equipped with a photo sensor operating in the 

appropriate wavelength. Some light meters are configured so that the photo sensor can be 

interchanged to allow for measuring illumination within a specific spectral wavelength band. 

Measurements are typically taken 6 inches to 1 foot above the ground with the photo sensor 

facing up. 

Adjustment and modification of the total lighting system after installation should be anticipated. 

It is not uncommon to discover during camera testing that there are unidentified reflections or 

bright spots that require correction. 

The horizontal and vertical illumination levels required for interior lighting are determined 

similarly to exterior illumination values. The geometry of walls, floor, and ceiling reflections will 

affect ambient light levels. 

Any interior lighting level suitable for human comfort and safety (e.g., between 30 and 100 f-c) 

will allow the use of a video camera with less sensitivity than is required for exterior video 

assessment applications. Energy savings can also be attained in interior spaces by illuminating 

a darkened room with near-infrared illumination sources and black-and-white cameras. The use 

of near-infrared illumination sources also provides a measure of covertness for the video 

assessment function in interior locations. 

The wiring circuit for a lighting system should be arranged so that failure of any one lamp will 

not leave a large portion of the perimeter or a critical location in darkness. Electrical feeder 

lines should be placed underground to minimize the possibility of sabotage or vandalism from 

outside the perimeter. Another advantage to underground wiring is reduced effects from 

adverse weather conditions. 

6.4.8.2 Lamp Types and Characteristics 

Primary lamp types include the following: 

 Incandescent: Light is emitted from a heated filament inside an evacuated globe. 

 Quartz Iodine: Light is generated as in an incandescent lamp, but the globe is filled 

with a halogen gas that regenerates the filament and allows higher intensity. 

 Fluorescent Lamp: Light is generated by an electric arc in a tube filled with mercury 

vapor. The low-pressure vapor emits ultraviolet radiation that is converted to visible light 

by fluorescent powders on the inner surface of the tube. 

 High-Intensity Discharge Lamp: The light energy is generated by direct interaction of 

an arc with the gas to produce visible light. High-intensity discharge lamps include 

mercury vapor lamps, metal halide lamps, and high- and low-pressure sodium lamps. 

Argon is normally added to aid starting, and various powders or vapors may be added to 

improve color rendition. 

 Light Emitting Diode (LED): The light energy is generated based on the light emitting 

diode solid-state technology. Lamps are usually constructed in cluster LEDs within 

suitable housing. Today, the LED lamp is mostly used for infrared illumination. 

However, LED may become more of a standard in the future for all types of lighting 

when considering the following advantages it offers over conventional lighting: 
 6-39 

 High efficiency—LEDs are available that reliably offer over 100 lumens per watt. 

 Life span—If properly engineered, LEDs can operate 50,000 to 60,000 hours. 

 Instant restrike—Lamps illuminate upon activation without delay. 

 Mercury free—Unlike fluorescent and most HID technologies, LEDs contain no 

hazardous mercury or halogen gases. 

 Tunable spectrum—LEDs can be tuned to emit light in a broad range of colors. 

Table 7 summarizes lamp characteristics for seven common bulb types. 

Table 7: Characteristics of Seven Common Types of Bulbs

 Incandescent Quartz 

Iodine 

Mercury 

Vapor 

(fluorescent)

Metal 

Halide 

HighPressure 

Sodium 

LowPressure 

Sodium 

LED 

Lamp 

Efficiency 

(lumens/ 

watt) 

12–20 20–23 40–65 80–100 95–130 131–183 70–100 

Approx. 

Life Span 

(hours) 

750–10,000 2,000 24,000 15,000 20,000 18,000 50,000 –

60,000 

Time 

Required 

for Full 

Output 

Immediate Immediate 3–7 

minutes 

3–5 

minutes 

3–4 

minutes 

8–15 

minutes Immediate

Spectrum 

Broad 

(Visible to NIR 

~ 400 to 1,000 

nm) 

Broad 

(Visible to 

NIR ~ 400 

to 1,000 nm) 

Blue 

Green 

Broad 

(Visible to 

NIR ~ 400 

to 1,000 nm)

Gold-Yellow 

Monochromatic 

Yellow 

Broad 

(Visible to 

NIR ~ 400 

to 1,000 nm)

6.4.9 Maintenance for Lighting Systems 

Periodic inspections should be made of all electrical circuits to replace or repair worn parts, 

tighten connections, and check insulation. Fixtures should be kept clean and correctly aimed to 

provide optimal service. 

Primary and alternate power sources should be identified. The following is a partial list of 

considerations: 

 The primary source is usually utility offsite power. 

 An alternate source such as supply UPS consisting of batteries and diesel-fuel-driven 

generators is provided where required and should do the following: 

 Provide required power automatically, without interrupting assigned illumination 

upon failure of primary power 

 Be adequate to power the entire lighting system 
 6-40 

 Be equipped with adequate fuel storage and supply 

 Be tested under load to ensure efficiency and effectiveness 

 Be located within a controlled area or hardened building inside the perimeter for 

additional security 

6.4.9.1 Measuring Perimeter Illumination Levels 

Facilities should adopt a standard method for taking initial and periodic perimeter illumination 

level measurements. This standard measurement will ensure that the light levels can be 

correlated to previous measurements for the purpose of determining the amount of illumination 

degradation as bulbs age. Tracking the illumination degradation of bulbs will allow maintenance 

personnel to predict when luminaires need to be cleaned and lenses or bulbs replaced. 

The measurement process requires two persons and the use of a 300-foot tape measure, a 

calibrated light meter, a 1-foot-high pedestal for attaching the light meter sensor, at least eight 

wooden blocks (see Figure 77), a clipboard, and a preprinted spreadsheet for recording 

measurements. Measurements are taken after sunset under darkened sky conditions after 

lights have been on sufficiently long to achieve full brightness. While the following instructions 

depict measurements for a 300-foot long area, the process can be applied to any length. 

Figure 77: Checking light levels using a light meter within a perimeter isolation zone during nighttime 

illumination. 
 6-41 

6.4.9.2 Preparation for Measuring Perimeter Illumination Levels 

The following procedure should be used to prepare for measuring perimeter illumination levels: 

(1) Beginning directly underneath one luminaire at the inner fence location (which will be 

called 0′ width and 0′ distance) and using a tape measure, place wooden blocks at 10-

foot intervals across the width of the perimeter toward the outer fence. (See Figure 78.) 

(2) As in Step 1, but at a 300-foot distance from the initial starting point along the inner 

fence, using a tape measure, place wooden blocks at 10-foot intervals across the width 

of the perimeter towards the outer fence. 

(3) With two persons, one at each end of the tape measure, extend the tape measure the 

entire 300-foot length to the second wooden block along the inner fence. Ensure that 

the tape measure is “face up” for its entire length. 

(4) Firmly attach the light meter sensor (face up) to the top of the pedestal with duct tape. 

0’width

10’width

20’width

Wooden blocks mark width of perimeter zone every 10’

at both 0’ and 300’ distances

Inner fence

Outer fence

300’

distance

30’ width

Width

Length (distance)

Tape measure use

Begin here

Figure 78: Preparation for measuring perimeter lighting illumination. 
 6-42 

6.4.9.3 Procedure for Measuring Perimeter Illumination Levels 

This procedure requires two persons; one person takes the measurement and the other person 

records the reading on a data sheet. 

(1) Beginning at the first measurement point, place the pedestal and sensor at the zero 

measurement point on the tape measure along the inner fence under the light fixture. 

(2) Read the illumination value from the light meter. Ensure that personnel or other 

obstructions are not casting a shadow on the light meter sensor. 

(3) Record the light meter reading on a data sheet (see a sample data sheet in Table 88). 

(4) Move to the 10-foot mark on the tape measure, and read and record the light meter 

reading on the data sheet. 

(5) Move to the 20-foot mark on the tape measure, and repeat the measurement and 

recording procedure. 

(6) Continue the measurement procedure until the 300-foot mark on the tape measure is 

reached. 

(7) Two persons, one on each end of the tape measure, move the tape measure to the two 

wooden blocks at the 10-foot distance from the inner fence. 

(8) Take measurements from the zero mark to the 300-foot mark as described in Steps 2 

through 7. 

(9) Move the tape measure to the blocks at the 20-foot and 30-foot distances (depending on 

the zone’s width) from the inner fence, and repeat the procedure described in Steps 2 

through 7. 

(10) When all the readings are taken, sum them and divide by the number of readings. For 

the example shown in Figure 79, the number of readings taken is 124 (31 readings per 

row multiplied by 4 rows). This is the average illumination level. 

(11) Ensure that the average illumination is greater than 1.0 f-c or 10 lux. 

(12) Find the highest reading and lowest reading on the data sheet. Divide the highest 

reading by the lowest reading; this is the light-to-dark ratio. 

(13) Ensure that the light-to-dark ratio is less than 6:1 (should be approximately 4:1 for initial 

installation readings). 

(14) As a second check of readings, divide the average illumination level, calculated in 

Step 11 above, by the lowest reading; this is the average-to-dark ratio. A well-designed 

lighting system will have an average light-to-dark ratio of approximately 2.5-to-1 (2.5:1) 

or less. 

(15) Document the readings and calculations for comparison to subsequent readings. 
 6-43 

(16) Compare calculations taken at initial installation with subsequent readings to determine 

illumination degradation. 

(17) Plot initial and subsequent average illumination, light-to-dark ratio, and average-to-dark 

ratio values after each set of measurements to show long-term trends in lighting 

degradation. 

0’ width

10’

distance

30’

distance

20’

distance

40’

distance

50’

distance

60’

distance

290’

distance

Inner fence

Outer fence

Wooden blocks mark width of perimeter zone every 

10’ at both 0’ and 300’ distances

10’ distances marked along perimeter zone length

Lighting measurements should be taken at each of these 

points

20’ width

10’ width

30’width

70’

distance

300’

distance

Figure 79: Points at which to measure light readings. 

Note: Every wooden block or red circle from the preceding diagram should have a 

coordinating measurement within one of the squares in the table on the next page. 
 6-44 

Table 8: Perimeter Light Measurements 

Width of Perimeter (as appropriate) 

 0′ 10 ′ 20 ′ 30 ′ 40 ′ 

L

E

N

G

T

H

O

F 

P

E

R

I

M

E

T

E

R

0′ 

10′ 

20′ 

30′ 

40′ 

50′ 

60′ 

70′ 

80′ 

90′ 

100′ 

120′ 

130′ 

140′ 

150′ 

Mark 

locations 

of lights 
 6-45 

6.5 Video Assessment System Testing

Testing requires that all the elements of the video assessment system work as integrated 

components, not individual parts. Therefore, each aspect of the video assessment system 

should be tested in concert. Video assessment systems that are integrated with intrusion 

detection systems should be tested in conjunction with each other as it is important to verify that 

these integrated systems are functioning and performing in the manner that they are interfaced. 

A regular program of testing system components is imperative for maintaining them in optimal 

operating order. Three types of testing need to be performed at different times in the life of a 

video assessment system: acceptance testing, performance testing, and operability testing. 

6.5.1 Acceptance Testing for Video Assessment Systems 

Upon receiving cameras for final installation, camera performance should be evaluated to 

determine conformity with the manufacturer’s specifications, compatibility with design criteria, 

and consistent performance from camera to camera. Experience has shown that final 

inspection at the manufacturer’s plant may produce cameras with nonequivalent performance 

for specific field applications and lighting conditions. On occasion, equipment arrives in 

damaged condition, or parts have shaken loose in transit. Operating equipment continuously 

(performing burn-in) for a few hundred hours before final installation will decrease issues 

associated with immediate equipment mortality after initial installation. 

Exterior cameras should be installed in accordance with the manufacturer’s requirements and 

focused at night while exposed to nighttime lighting conditions. Some cameras are shipped 

prefocused to specified distances. However, the environment in which these cameras are 

focused may not be the same as the operating environment at the facility. Initial camera setup 

should be followed by indoor and outdoor testing to confirm that the cameras perform as 

expected. Final adjustments to camera focus and video image adequacy under nighttime 

lighting conditions should be made. The video images produced by the cameras should not 

vary much in picture quality between daytime and nighttime operation. Washed-out images 

during the day or dark, low-contrast images at night are indications that cameras are not 

performing to intended requirements. 

Cameras should be checked for resolution and complete coverage of the assessed zone to 

ensure that there are no detection areas in a zone that the camera cannot see. One simple 

method of checking camera resolution is to use 1-foot-sized triangular, circular, and square 

targets. The targets, painted white on one side and black on another, are placed at the end of 

an assessment zone, and an alarm station operator should correctly identify the target shapes. 

One-foot targets simulate the frontal cross-section of a crawling person. The use of a large field 

resolution chart such as a Rotakin can also be used to provide more quantifiable information of 

camera resolution. In addition, the alarm station operator should be able to see the feet of an 

individual standing at both the inner and outer fence when the operator is standing at the 

beginning of the assessed zone. This test should be performed on live video from the cameras, 

as well as on playback video from the video recording device for each assessment zone. In 

interior spaces, particular attention should be paid to the location of equipment or other objects 

that might occlude camera view or create shadows or blind spots. 

Video system speed of response should be tested to ensure that alarm assessment and video 

recording of an intrusion detection zone occurs within 1 or 2 seconds of alarm annunciation. 
 6-46 

Other performance tests include a determination of the maximum number of concurrent alarms 

that can be processed, logged, and recorded at the same time and the amount of assessment 

delay occurring if more than one alarm occurs concurrently. The desired specifications and 

statement of acceptance testing requirements should be included as part of the terms and 

conditions of system purchase from the security systems integrator. 

Conducting equipment incoming inspection, burn-in, and adjustments before actual use should 

minimize maintenance and failure problems in the short term. A dated maintenance log should 

be kept to document occurrences of problems, problem resolution, and if recurring problems 

occur, long-term fixes or equipment replacements undertaken to remediate repetitive problems. 

Maintenance cycles can be established for the performance of repetitive maintenance activities 

and equipment replacement activities as a result of the data collected on the performance and 

failures occurring during system operation. This practice will substantially reduce repair time 

and identify substandard equipment performance. 

Equipment spares should be planned for at the design phase of the video assessment system 

so that failures can be immediately replaced. The spares inventory should be replenished as 

spare parts are put into service. 

One copy of the manufacturers’ equipment documentation should be kept in a central document 

storage location and another copy should be kept by the security equipment maintenance 

organization. Modifications to the security system (as initially installed or documented) should 

be documented and stored at these two locations. 

Acceptance testing for the video assessment system is the most encompassing because 

baseline performance and operability are determined and documented. Acceptance tests will 

uncover operational and functionality issues that need to be addressed to ensure system 

operation in accordance with design specifications. 

Use the following guidelines to perform acceptance testing: 

6.5.1.1 Cameras and Digital Video Recorders Used To Play Back Camera Images 

(1) Ensure that each camera produces a video image on the alarm station monitors and that 

each camera channel produces video playback images for that channel on the alarm 

station monitors. 

(2) Ensure that camera channel numbering is arranged in a logical rather than haphazard 

order. For example, cameras for adjacent perimeter sectors should be sequentially 

numbered, and cameras inside buildings should be numbered according to a logical flow 

traversing through the building. For DVRs, ensure that the numbering of DVR camera 

input channels agrees with the live camera channels indicated on the alarm station 

monitors. 

(3) With multiple individuals in the field communicating with alarm station operators, ensure 

that the camera image displayed on the monitor and recorded on the digital recorder is 

the correct one for the assessed space indicated. The alarm station operators should 

observe the person in the field. Also, ensure that playback of video from the recorder 

shows the correct field location for the camera channel being tested. 
 6-47 

(4) If camera images have graphic legends displayed on the monitor, ensure that the 

graphic legend is labeled correctly for the camera channel being tested. 

(5) Ensure that camera resolution is sufficient for intruder classification and that cameras 

are in focus at night with nighttime illumination. To perform this test, one individual in the 

field places a 1-foot triangle, circle, and square at ground level at the end of the 

assessment zone or area. The alarm station operator, communicating with the individual 

in the field via two-way radio, should correctly identify the order of the triangle, circle, 

and square. Alternately, using a field resolution chart calibrated for the distance from the 

camera, the alarm station operator should be able to accurately observe four distinct 

lines on the resolution chart at the calibrated position on the chart. 

(6) Ensure that video recorder playback resolution is sufficient for intruder classification. 

Repeat the procedure for determining camera resolution (in the preceding step) to 

ensure video recorder playback resolution. 

(7) Ensure that exterior cameras are focused so that the camera image is “in focus” at both 

the near and far fields of view. For example, check to ensure that the video image at 

both the beginning and end of an assessment zone are in focus. 

(8) In exterior perimeter isolation zones, ensure that cameras are aimed so that the entire 

perimeter width can be observed on the alarm station monitors and in the recorded 

video. Camera aim can be tested by using two orange cones and two fiberglass rods in 

the following fashion. Two 2-foot-long fiberglass rods with a reflector at one end are 

fabricated with a clamping mechanism (like a battery jumper cable clamp) for attaching 

to the top horizontal pipe of the perimeter fence (rods are available at a local home 

building materials store). The rods are attached to the top of the inner and outer 

perimeter fences at the beginning of each perimeter isolation zone. The two cones are 

placed along the perimeter side of the inner and outer perimeter fences at the beginning 

of each assessment zone. The alarm station operator should be able to see the bottoms 

of the cones at the beginning of the sector, as well as the reflectors at the top of the 

fence attachment rods. 

(9) Ensure that a low-profile human observed on the alarm station monitors (and on the 

playback of recorded video) can be classified at the far end of each perimeter 

assessment zone. This should be tested at night, at the inner and outer fence line inside 

the perimeter and at the center of the perimeter. The test subject should be a small 

individual who performs a belly crawl with his or her head toward the camera. The alarm 

station operator observing the monitor (and the playback of recorded video) should be 

able to determine that the simulated intruder can be observed and accurately classified. 

(10) During bright sunlight and during nighttime illuminated conditions, observe each exterior 

camera on the alarm station monitors (and on the playback of recorded video), and 

ensure that images from each camera have approximately the same brightness and 

contrast and that monitor images of assessment zones do not have bright spots or dark 

spots. For images that are too bright, too dark, or lacking in contrast, camera or lens 

adjustment or replacement may be required. For analog camera systems, video 

transmission or communication modules may also be the source of video brightness 

anomalies. 

(11) Observe the scene from each interior camera on the alarm station monitors and ensure 

that images from each camera have approximately the same brightness and contrast. 
 6-48 

For images that are either too bright, too dark, or lacking in contrast, camera or lens 

adjustment or replacement may be required. For analog camera systems, video 

transmission or communication modules may also be the source of video brightness 

anomalies. 

(12) Observe interior and exterior cameras on the alarm station monitors and ensure that 

images are clear and crisp and do not have fuzzy or flickering images. 

6.5.1.2 Camera Tests 

(1) Ensure that exterior cameras are tilted down and do not view above the horizon at the 

camera’s far field of view. 

(2) Ensure that bright spots, shiny reflections, or glare from luminaires does not appear in or 

cast a bright image in a camera’s field of view. 

(3) Ensure that large objects, such as electrical junction boxes that a person could hide 

behind, are not in an exterior camera’s fields of view. 

(4) Check all fasteners for the camera tower and mount to ensure they are secure and there 

is no movement caused by loose fasteners. 

(5) Ensure that the camera, enclosure, and mount are firmly affixed and not affected by 

wind causing movement of camera. 

(6) For camera enclosures with external sunshades, ensure the enclosures have sunshades 

that extend at least 2 inches beyond the front of the camera enclosure. 

(7) During blowing snow conditions, ensure that enclosure heaters melt the snow 

accumulation on the enclosure front cover glass without creating an accumulation of ice 

on the front cover glass. 

6.5.1.3 Intrusion Alarm and Assessment Camera Interface Tests 

Ensure that intrusion alarms in assessed areas trigger the appropriate camera’s video to appear 

on the alarm station monitors (and on the playback of recorded video). While communicating 

with the alarm station operator using a two-way radio, an individual in the field should trigger an 

alarm in each intrusion detection zone. The alarm station operator should ensure that the 

assessment video displayed because of the alarm is from the correct camera for the zone in 

alarm and that the assessment video appears on the monitor within seconds. If an intrusion 

detection zone has multiple sensors, an intrusion alarm and video verification should be 

performed for each sensor. 

6.5.1.4 Camera Lighting Tests 

Turn off nighttime illumination, and ensure that a “loss of video contrast” alarm occurs for each 

camera. 
 6-49 

6.5.1.5 Power Tests 

(1) Disconnect or switch the main source of power to the video assessment system to 

simulate loss of offsite power, and ensure that the UPS and diesel generator maintain 

uninterrupted power to the intrusion detection and assessment systems for the 

appropriate timeframe (will vary with the facility.) 

(2) Disconnect individual cameras at field camera junction boxes, and ensure that a “loss of 

video” alarm occurs for each camera. 

6.5.1.6 Tampering and Accidental Disconnection Tests 

(1) Cover the front of the camera enclosure, and ensure that a “loss of video contrast” alarm 

occurs for each camera. 

(2) Shine a bright light into the front of each camera, and ensure that a “loss of video 

contrast” alarm occurs for each camera. 

(3) Disconnect the video signal cable from each analog camera, and ensure that a “loss of 

video” alarm occurs for each camera. 

(4) Disconnect the fiber-optic video transmission cable (fiber) for each camera, and ensure 

that a “loss of video” alarm occurs for each camera. 

(5) Disconnect the Ethernet cable from each digital camera, and ensure that a “loss of 

video” alarm occurs for each camera. 

(6) Disconnect the camera Ethernet cable to Ethernet switches carrying video signals, and 

ensure that a “loss of video” alarm occurs for all cameras connected to the switch. 

(7) Disconnect the power cable to Ethernet switches carrying video signals, and ensure that 

a “loss of video” alarm occurs for all cameras connected to the switch. 

(8) Simultaneously create intrusion alarms in multiple (two through five) adjacent and 

nonadjacent perimeter intrusion detection zones. Ensure that the alarm assessment 

video cues the recorded and live (pre- and post-alarm) video and displays the video for 

each of the alarming zones. 

6.5.1.7 Camera Towers 

Ensure that camera towers are properly grounded and have a lightning air terminal at the top of 

the tower. Also ensure that the tower and lightning rod (air terminal) have cables exothermically 

bonded to a ground rod at each tower. Resistance from the lightning rod and the tower to the 

ground rod cable attaching point must be less than 1 ohm. 

6.5.1.8 Camera Tower Junction Boxes and Field Distribution Junction Boxes 

Ensure that the camera tower junction box and field distribution junction box create tamper 

alarms when each enclosure is opened. Also ensure that the alarm station tamper alarm 

notification indicates the opening of the correct junction box. To accomplish this test, an 

individual in the field communicates with the alarm station operator using a two-way radio. The 
 6-50 

individual in the field opens each camera tower junction box and field distribution panel (one at a 

time). The alarm station operator verifies that the correct tamper alarm message occurs for the 

box opened. After each test, the junction box door is reclosed. The alarm station operator 

observes that the tamper alarm can be cleared after the junction box door is closed. 

6.5.1.9 Shadow and Light Variation Determinations 

(1) During nighttime illumination of perimeter isolation zones, observe monitor images of 

each assessed zone to ensure that fences are vertically perpendicular to the ground so 

that a shadow alongside the base of the perimeter side of the fence is not present. 

(2) Ensure that buildings and large equipment enclosures do not cast a shadow across the 

perimeter isolation zone during either daytime or nighttime hours. Shadow areas reduce 

image contrast and video assessment capability. 

6.5.1.10 Camera Brightness 

(1) Ensure that nighttime bright light illumination from adjacent buildings or parking lots does 

not create bright spots on the floor of the perimeter. 

(2) Ensure that camera brightness is consistent during changing daylight brightness 

conditions, particularly during morning and evening hours. This ensures that camera 

electronics and auto-iris lens controllers are compensating properly for changing 

illumination levels. This condition is normally observed as a video image that is either 

brighter or darker than other camera images. For images that are too bright, too dark, or 

lacking contrast, camera or lens adjustment or replacement may be required. For 

analog camera systems, video transmission or communication modules may also be the 

source of video brightness anomalies. 

(3) Ensure that camera brightness is not oscillating between two auto-iris positions. This is 

observed as an oscillating lighter to darker camera image. This effect can be caused by 

dust in the auto-iris lens mechanism or improper combination of lens control and camera 

amplifier electronics parameter adjustments. Camera or lens adjustment or replacement 

may be required. 

6.5.2 Operability Testing 

Operability testing for the video assessment system is an ongoing set of tests to ensure that the 

video assessment system continues to function properly. Operability tests identify sources of 

system degradation and nonfunctionality requiring immediate attention and remediation. Tests 

are to be conducted for all camera locations. It is recommended that these tests be performed 

in conjunction with intrusion detection system and component tests to verify that both systems 

are operating and interfacing as required. Several of these tests repeat the acceptability tests. 

(1) Ensure that intrusion alarms in assessed areas cause the appropriate camera’s video to 

appear on the alarm station monitor (and on the playback of recorded video). While 

communicating with an alarm station operator using a two-way radio, an individual in the 

field triggers an alarm in an intrusion detection zone. The alarm station operator 

ensures that the assessment video resulting from the alarm is from the correct camera 

for the zone in alarm and that the assessment video appears on the alarm station 
 6-51 

monitors within seconds. If multiple sensors are in an intrusion detection zone, an 

intrusion alarm is created, and video verification is performed for each sensor. 

(2) Ensure that the graphic legend is labeled correctly for the alarming camera channel 

being tested, and ensure that the graphic legend is stable and not “jittering” on the 

monitor screen. 

(3) Ensure that interior cameras produce an image that is “in focus.” Ensure that exterior 

cameras are “in focus” at both the near and far fields of view. Ensure that the video 

image at both the beginning and end of an assessment zone are in focus. Ensure that 

camera images are clear and crisp and do not have fuzzy or flickering images. 

(4) Ensure that camera focus and video recorder playback quality is sufficient for human 

intruder classification. One individual in the field places a 1-foot triangle, circle, and 

square at ground level at the end of the assessment zone or area. The alarm station 

operator should correctly identify the order of the triangle, circle, and square by 

observing live camera video on the alarm station monitor and playback video images. 

(5) The following is an alternate method. At night, at the inner and outer fence line inside 

the perimeter and at the center of the perimeter, a small individual “on all fours,” with his 

or her head towards the camera, moves sideways in the camera field of view. An alarm 

station operator observing the monitor in the alarm station should be able to determine 

that the simulated intruder can be observed and accurately classified. 

(6) In exterior perimeter isolation zones, ensure that cameras are aimed so that the entire 

perimeter width can be observed on the alarm station monitor. For this test, two orange 

cones are required. The two cones are placed along the perimeter side of the inner and 

outer perimeter fences at the beginning of each assessment zone. The alarm station 

operator should be able to see the bottoms of the cones at the beginning of the sector. 

(7) For interior cameras and for exterior cameras, during bright sunlight and during nighttime 

illumination conditions, observe camera images on the alarm station monitor and ensure 

that camera images have approximately the same brightness and contrast and that 

monitor images of assessment zones do not have bright spots or dark spots. For 

images that are too bright, too dark, or lacking in contrast, camera or lens adjustment or 

replacement may be required. For analog camera systems, video transmission or 

communication modules may also be the source of video brightness anomalies. 

(8) Ensure that camera brightness is not oscillating between two auto-iris positions. This is 

observed as an oscillating lighter-to-darker camera image. This effect can be caused by 

dust in the auto-iris lens mechanism or improper combination of lens control and camera 

amplifier electronics parameter adjustments. Camera or lens adjustment or replacement 

may be required. 

6.5.3 Performance Testing 

Performance testing for the video assessment system is a set of tests performed to ensure that 

the entire video assessment system is performing to design requirements and all functions are 

operating properly. Performance tests are an indepth set of tests to identify sources of system 

degradation and nonfunctionality needing repairs to bring the system back to initial performance 
 6-52 

specifications. Tests are to be conducted for all camera locations. It is recommended that 

these tests be performed on the entire set of camera-assessed areas on an annual schedule. 

(1) Ensure that each camera produces a video image on the monitor (and on the playback 

of recorded video). 

(2) Ensure that intrusion alarms in assessed areas cause the appropriate camera’s video to 

appear on the alarm station monitor and to be recorded on the video recorder. While 

communicating with an alarm station operator using a two-way radio, an individual in the 

field triggers an alarm in an intrusion detection zone. The alarm station operator 

ensures that the live video and playback of recorded assessment video resulting from 

the alarm is from the correct camera for the zone in alarm and that the assessment 

video appears on the alarm station monitor within seconds. If multiple sensors are in an 

intrusion detection zone, an intrusion alarm is created, and video verification is 

performed for each sensor. 

(3) Ensure that the graphic legend is labeled correctly for the alarming camera channel 

being tested, and ensure that the graphic legend is stable and not “jittering” on the 

monitor screen. 

(4) Ensure that interior cameras produce an image that is in focus. Ensure that exterior 

cameras are in focus at both the near and far fields of view. Ensure that the video 

image at both the beginning and end of an assessment zone is in focus. Ensure that 

camera images are clear and crisp and do not have fuzzy or flickering images. 

(5) Ensure that camera focus and video recorder playback quality are sufficient for human 

intruder classification. One individual in the field places a 1-foot triangle, circle, and 

square at ground level at the end of the assessment zone or area. While 

communicating with the individual in the field via two-way radio, an alarm station 

operator observes live camera video on an alarm station monitor and video recorder 

playback images and should correctly identify the order of the triangle, circle, and 

square. 

(6) In exterior perimeter isolation zones, ensure that cameras are aimed so that the entire 

perimeter width can be observed on the alarm station monitor. For this test, two orange 

cones and two fiberglass rods are required. Two 2-foot-long fiberglass rods with a 

reflector at one end are fabricated with a clamping mechanism (like a battery jumper 

cable clamp) for attaching to the top horizontal pipe of the perimeter fence (rods are 

available at local home building materials stores). The rods are attached to the top of 

the inner and outer perimeter fences at the beginning of each perimeter isolation zone. 

The two cones are placed along the perimeter side of the inner and outer perimeter 

fences at the beginning of each assessment zone. The alarm station operator should be 

able to see the bottoms of the cones at the beginning of the sector, as well as the 

reflectors at the top of the fence attachment rods. 

(7) Ensure that a low-profile human observed on an alarm station monitor can be classified 

at the far end of each perimeter assessment zone. At night, at the inner and outer fence 

line inside the perimeter, and at the center of the perimeter, a small individual performs a 

belly crawl with his or her head toward the camera. The alarm station operator 

observing the monitor should be able to determine that the simulated intruder can be 

observed and accurately classified. 
 6-53 

(8) For interior cameras and for exterior cameras, during bright sunlight and during nighttime 

illuminated conditions, observe camera images on the alarm station monitor and ensure 

that camera images have approximately the same brightness and contrast and that 

monitor images of assessment zones do not have bright spots or dark spots. For 

images that are too bright, too dark, or lacking contrast, camera or lens adjustment or 

replacement may be required. For analog camera systems, video transmission or 

communication modules may also be the source of video brightness anomalies. 

(9) Ensure that camera brightness is not oscillating between two auto-iris positions. This is 

observed as an oscillating lighter-to-darker camera image. This effect can be caused by 

dust in the auto-iris lens mechanism or improper combination of lens control and camera 

amplifier electronics parameter adjustments. Camera or lens adjustment or replacement 

may be required. 

(10) Ensure that a low-profile human observed on the playback of video taken during Test 8 

above can be classified at the far end of each perimeter assessment zone. At night, at 

the inner and outer fence line inside the perimeter, and at the center of the perimeter, a 

small individual performs a belly crawl with his or her head toward the camera. The 

alarm station operator observing the playback of belly crawl activities should be able to 

determine that the simulated intruder can be observed and accurately classified. 

(11) During bright sunlight and during nighttime conditions, observe each exterior camera on 

the alarm station monitor and ensure that images from each camera have approximately 

the same brightness and contrast and that monitor images of assessment zones do not 

have bright spots or dark spots. For images that are too bright, too dark, or lacking 

contrast, camera or lens adjustment or replacement may be required. For analog 

camera systems, video transmission or communication modules may also be the source 

of video brightness anomalies. 

(12) Observe interior and exterior cameras on an alarm station monitor, and ensure that 

images are clear and crisp and do not have fuzzy or flickering images. 

(13) Ensure that exterior cameras are tilted down and do not view above the horizon at the 

camera’s far field of view. 

(14) Ensure that bright spots, shiny reflections, or glare from luminaires does not appear in or 

cast a bright image in a camera’s field of view. 

(15) Ensure that large objects, such as electrical junction boxes that a person could hide 

behind, are not in an exterior camera’s field of view. 

(16) Check all fasteners for the camera tower and mount to ensure they are secure and there 

is no movement caused by loose fasteners. 

(17) Ensure that the camera, enclosure and mount are firmly affixed and not affected by wind 

causing movement of camera. 

(18) During blowing snow conditions, ensure that enclosure heaters melt any snow 

accumulation on the enclosure’s front cover glass without creating an accumulation of 

ice on the front cover glass. 
 6-54 

(19) Turn off nighttime illumination, and ensure that a “loss of video contrast” alarm occurs for 

each camera. 

(20) Disconnect or switch the main source of power to the video assessment system to 

simulate a loss of offsite power, and ensure that the UPS and diesel generator maintain 

uninterrupted power to the intrusion detection and assessment systems for the 

appropriate timeframe (will vary with the facility). 

(21) Disconnect power to individual cameras at field camera junction boxes, and ensure that 

a “loss of video” alarm occurs for each camera. 

(22) Cover the front of the camera enclosure, and ensure that a “loss of video contrast” alarm 

occurs for each camera. 

(23) Shine a bright light into the front of each camera, and ensure that a “loss of video 

contrast” alarm occurs for each camera. 

(24) Disconnect the video signal cable from each analog camera, and ensure that a “loss of 

video” alarm occurs for each camera. 

(25) Disconnect the fiber-optic video transmission cable (fiber) for each camera, and ensure 

that a “loss of video” alarm occurs for each camera. 

(26) Disconnect the Ethernet cable from each digital camera, and ensure that a “loss of 

video” alarm occurs for each camera. 

(27) Disconnect the camera Ethernet cable to Ethernet switches carrying video signals, and 

ensure that a “loss of video” alarm occurs for all cameras connected to the switch. 

(28) Disconnect the power cable to Ethernet switches carrying video signals, and ensure that 

a “loss of video” alarm occurs for all cameras connected to the switch. 

(29) Simultaneously create intrusion alarms in multiple (two through five) adjacent and 

nonadjacent perimeter intrusion detection zones. Ensure that the alarm assessment 

video queues the recorded and live (pre- and post-alarm) video and displays the video 

for each of the alarming zones. 

(30) Ensure that camera towers are properly grounded, have lightning air terminals at the top 

of each tower, and the tower and lightning rod (air terminal) have cables exothermically 

bonded to a ground rod at each tower. Resistance from the lightning rod and the tower 

to the ground rod cable attaching point must be less than 1 ohm. 

(31) Ensure that the camera tower junction box and the field distribution junction box create 

tamper alarms when each enclosure is opened. Ensure that the alarm station receives 

the tamper alarm notification and indicates the opening of the correct junction box. An 

individual in the field communicates with an alarm station operator using a two-way 

radio. The individual in the field opens each camera tower junction box and field 

distribution panel (one at a time). The alarm station operator verifies that the correct 

tamper alarm message occurs for the box opened. After each test, the junction box door 

is reclosed. The alarm station operator observes that the tamper alarm can be cleared 

after the junction box door is closed. 
 6-55 

(32) During nighttime illumination of perimeter isolation zones, observe monitor images of 

each assessed zone to ensure that fences are vertically perpendicular to the ground so 

that a shadow along the base of the perimeter side of the fence is not present. 

(33) Ensure that buildings and large equipment enclosures do not cast a shadow across the 

perimeter during daytime or nighttime hours. Shadow areas reduce image contrast and 

video assessment capability. 

(34) Ensure that nighttime bright light illumination from adjacent buildings or parking lots does 

not create bright spots on the floor of the perimeter. 

6.6 Maintenance

A video assessment system requires regular maintenance to ensure a high level of performance 

and reliability. 

Maintenance should be performed according to a defined schedule. If performance or 

operability testing show degraded system performance, the maintenance schedule should be 

adjusted accordingly. 

Maintenance procedures and equipment needed to maintain the video assessment system 

should be considered during the design phase of the system. The long-term operability and 

performance of the system will depend on effective maintenance. Spare part purchases should 

be made at the same time as the primary equipment purchases to ensure video assessment 

system operational continuity and parts interchangeability. The level of maintenance to be 

performed on site should be decided early in the design process. This level will determine the 

type and quantity of spare parts to be purchased and the level of maintenance and repair 

functions required. 

A staff of qualified maintenance personnel is necessary for the assessment system to continue 

performing at the level established during the system design. Ideally, an experienced 

maintenance staff should be knowledgeable about the system configuration, subsystem 

component location, cable routing, installation, checkout, and troubleshooting procedures. 

A maintenance log of all equipment repairs and adjustments should be kept to provide a 

historical record of the actions taken to correct specific problems. Maintenance trends can be 

established to identify recurring problems and corrective actions to eliminate repetitive 

occurrences of the same problem. This can substantially reduce repair time and identify 

equipment performing in a substandard manner. 

Adequate maintenance cannot be performed without adequate equipment documentation. 

Maintenance and operations manuals should be purchased at the time of equipment 

procurement. Complete documentation should include theory of operation, functional block 

diagrams, cabling diagrams, schematic diagrams, and parts lists with manufacturers’ or 

commercial equivalent part numbers.

7-1 

7. OWNER-CONTROLLED AREA SURVEILLANCE 

7.1 Overview of Concepts and Definitions

Often, the owner-controlled area of a facility is larger than the section of the facility that is 

enclosed within protected area (PA) perimeter fencing. (Refer to Figure 80.) Long-distance 

surveillance technologies are usually employed to survey the owner-controlled area that resides 

outside the PA perimeter fencing for possible early warning or detection of intruders. 

Figure 80: For the example facility, the owner-controlled area, shown in green, is much larger than the 

security area that is enclosed within perimeter fencing. Real-time surveillance across the owner-controlled 

area can be challenging, especially given widely varying terrain. 

Key elements common to many long-distance surveillance devices that should be understood 

when considering the purchase of real-time, surveillance-type devices include magnification, 

objective lens diameter, and field of view. 

7.1.1 Magnification 

This element determines the degree to which the object being viewed is enlarged. Two 

numbers are associated with binoculars, for example, 7  50. The “7” represents the amount of 

magnification; the object being viewed will be 7 times larger than if viewed by the unaided eye. 

The greater the magnification or power, the smaller the field of view and the less bright the 

image will be. It is recommended that any item over 10 should be mounted on a tripod or 

similar device. Spotting scopes typically have three numbers: 15–45  80. The first two 

numbers “15–45” represent the magnification range of the scope, and the third number (“80”) 

relates to the diameter of the objective lens. 
7-2 

7.1.2 Objective Lens Diameter 

Objective lenses are the front lenses of binoculars. The diameter of these lenses, given in 

millimeters, is the second number associated with binoculars and the third number associated 

with spotting scopes. For example, for the 7  50 binoculars, the “7” is the magnification or 

power, and the “50” represents the diameter in millimeters of the objective lenses. The diameter 

of the objective lens determines the light-gathering ability, which equates to brightness and 

usability of an image being viewed under certain conditions. 

7.1.3 Field of View 

The size of an area that can be seen while looking through a surveillance device is referred to 

as the “field of view.” Field of view is related to magnification; the higher the magnification, the 

smaller the field of view. A large field of view is desirable if a broad area is under surveillance. 

A large field of view provides the viewer with the capability to continually observe activity with 

minimum viewing adjustments and loss of observation. With a smaller field of view, the object 

being viewed is likely to move beyond the field of view causing a loss of observation and the 

need to continuously adjust. The same is true when the user is moving. 

The following types of devices are readily available that will allow a facility to perform 

surveillance at different distances and under different conditions: 

 Binoculars 

 Spotting scopes 

 Night vision devices 

 Thermal imagers 

 Enhanced night vision devices, which use a fusion of night vision and thermal 

technologies 

The U.S. Department of Defense has done extensive testing of surveillance devices. The exact 

model of a surveillance device to be implemented at a particular facility will depend on the site 

conditions and the surveillance objectives to be met. 

7.2 Binoculars

7.2.1 Principles of Operation 

Binoculars provide the user with the ability to use both eyes to peer through two identical 

mirror-symmetrical telescopes. These telescopes magnify distant objects up to 10 times. 

Because both eyes are used, binoculars allow for depth perception, which helps provide a 

three-dimensional image. Devices that employ only one eye do not provide depth perception. 

Binoculars hold the two telescopes such that a hinge between them allows the distance 

between the two telescopes to be adjusted to the individual user. A wheel allows the user to 

focus both telescopes similarly by changing the distance between the eyepieces and the 

objective lenses. Some binoculars are available that allow the user to focus the two telescopes 

individually. 

The quality of a pair of binoculars is predominantly determined by the quality of the lenses used, 

which affects the cost of a particular device. Precision-ground lenses can provide a clarity that 
7-3 

is not available with cheaper lenses. While the human eye can compensate for poor quality 

glass for short periods of time, the user will likely experience extreme eye fatigue if more than a 

few minutes of use is required. 

Hand-held binoculars are limited to a 10 times magnification because higher magnification, 

without the use of a tripod or similar mounting device for image stabilization, results in image 

vibration/destabilization. The vibration/destabilization is a result of the normal physiology of the 

body, such as heart and breathing rate. 

Binoculars with high-quality lenses will actually help the human eye to see better at night than 

the unaided eye. (High-quality lenses increase the light-gathering ability of the binoculars, 

which in turn increases the brightness relative to the human eye at the objective.) 

7.2.2 Types of Binoculars Available 

A wide variety of binoculars are available that support a wide variety of applications. Binoculars 

that are considered “general purpose” are typically not appropriate for use by a security 

organization of a large facility. “Long-range observation,” “military,” and “range finder” types are 

usually considered for security applications. 

7.2.3 Characteristics and Applications 

Most long-range observation binoculars provide good clarity for long-term use. One problem in 

using such binoculars is that below-optimal lighting conditions can significantly degrade the 

scene viewed. 

Military-rated binoculars generally provide good optics and receive extensive testing, including 

shock tests, to ensure that they will function as intended under most conditions. 

Range-finder binoculars can identify the distance between the user and the object being viewed 

and are the most expensive type of binocular. 

7.2.4 Testing 

Testing on a weekly basis is recommended to ascertain that the device operates as advertised 

by the manufacturer. If the device is dropped, the user should test the device as soon as 

possible. 

7.2.5 Maintenance 

Most binoculars require daily cleaning of the lens using a cleaner and soft cloth recommended 

by the manufacturer. Devices that have an on/off switch also require routine checks and 

replacement of batteries. 
7-4 

7.3 Spotting Scopes

7.3.1 Principles of Operation 

A spotting scope is a small type of telescope that can be used during daylight conditions and 

can be used any time more magnification is needed than binoculars can provide. 

Two factors determine the amount of magnification that can be used in a spotting scope: 

atmospheric conditions and the optical system. 

The view through a spotting scope is significantly impacted by heat waves, dust, humidity, glare, 

wind, and air currents. The greater the magnification of a device, the greater the degradation of 

the performance of the spotting scope during such conditions. High altitudes and dry climates 

favor higher magnification, while low altitudes and wet, humid climates discourage high 

magnification. 

The optical system of a scope is a determining factor in what and how well the user will be able 

to see. Image quality is directly related to cost. The inexpensive spotting scopes, regardless of 

size or type, lose image quality as magnification increases. Premium-grade scopes will lose 

very little image quality as the magnification increases. 

The magnification capabilities of spotting scopes range from 10 up to 400 times. 

7.3.2 Characteristics and Applications 

A quality spotting scope used under good atmospheric conditions can provide high-quality 

scenes of objects extremely far away. Because of the sizes of lenses needed for the higher 

magnifications of a spotting scope, these devices can become quite large and cumbersome. 

Most spotting scopes must be mounted on a tripod or other device to keep them still enough to 

use. 

The higher magnifications and greater distances create a much smaller field of view for the 

user. Adequate lighting at great distances can also hinder the usability of a scope. 

7.3.3 Testing 

Testing on a weekly basis is recommended to ascertain that the device operates as advertised 

by the manufacturer. If the device is dropped, the user should test the device as soon as 

possible. 

7.3.4 Maintenance 

Spotting scopes require daily cleaning of the lens using a recommended cleaner and soft cloth. 
7-5 

7.4 Night Vision Devices

7.4.1 Principles of Operation 

Night vision devices (also referred to as night vision goggles) operate by amplifying available 

light. Such devices can take small amounts of light, such as starlight, moonlight, or area-related 

ambient light, and convert the light energy into electrical energy. Electrons pass through a thin 

disk containing over 10 million channels. As the electrons pass through these channels, they 

strike the walls, releasing thousands of more electrons. These multiplied electrons bounce off a 

phosphor screen, which converts them back into photons and enables the user to see an 

accurate nighttime view. 

Until recently, all image-intensified night vision devices had one attribute in common: they all 

produced a green image output. A few manufacturers are currently marketing what they call a 

full-color device. 

7.4.2 Types of Night Vision Devices Available 

Night vision devices are categorized by generations which reflect the level of technology in their 

development. 

 Generation 0: (1950s) These devices required an infrared light source to illuminate the 

observation area. 

 Generation 1: (1960s) This was the era of the “starlight scope.” Still in limited use 

today, such scopes comprise three intensifier tubes connected in series. These are 

bulky and heavy in comparison to today’s technology. 

 Generation 2: (1970s) Use of the microchannel plate (MCP) eliminated the need for 

back-to-back tubes. Size, weight and image quality were greatly enhanced. 

 Generation 3: (1970s–1980s) Two major advances in materials led to an increase in 

detection at greater distances in much darker conditions and a significant increase in 

operational life span of the night vision device. Gallium arsenide photocathode and the 

ion barrier film on the MCP enabled these advancements. I2 (I-squared—Image 

Intensification) is a common name for the Generation 3 and 4 technologies. 

 Generation 4: (1998) Filmless technology with no ion barrier or protective coating on 

the MCP0 created a 20-percent increase in performance. Unfortunately, the tubes 

showed immediate degradation since the protective film for the photocathode had been 

removed. This degradation also affected the life span, reducing it below the required 

10,000-hour active life requirement within some branches of the military. 

Other items to note are the following: 

 AN/PVS (Army Navy/Passive Vision Sight) is a designation prefix for night vision 

equipment in the U.S. Department of Defense (DOD). 
7-6 

 Variable gain is an improvement capability that enhances the goggles’ capability in 

variable lighting conditions. It provides the user with a rheostat to limit the amount of 

incoming light. 

7.4.3 Characteristics and Applications 

Night vision devices can provide valuable images during night-time hours that could never be 

seen without such a device. Using a night vision device, the distinct image of a moving human 

can be captured from a distance of 1,000 to over 2,000 meters (3280 to over 6560 feet). 

One weakness in the use of night vision devices is the lack of color in the images. Acceptable 

clarity because of a lack of depth perception in some models can be a concern. Furthermore, a 

would-be adversary could use particular camouflage that would prevent the user of a night 

vision device from spotting the adversary. The field of view that the device provides should also 

be evaluated and should be consistent and appropriate for the type of surveillance and 

observation required. 

7.4.4 Testing 

Testing on a weekly basis is recommended to ascertain that the device operates as advertised 

by the manufacturer. If the device is dropped, the user should test the device as soon as 

possible. 

7.4.5 Maintenance 

Most night vision devices require daily cleaning of the lens with a cleaner and soft cloth 

recommended by the manufacturer. Batteries need to be routinely checked and replaced. 

7.5 Thermal Imager Equipment

7.5.1 Principles of Operation 

Unlike a night vision device, a thermal imager needs no light to operate. Thermal imager 

devices can detect (see) heat and the movement of heat. Thermal imagers work in the 3 micron 

to 30+ micron wavelength of the infrared spectrum. This wavelength can be termed as thermal 

infrared. Thermal infrared is emitted by an object, not reflected off of an object. This emission 

is picked up by the special lens of thermal vision equipment, focused, and then scanned by a 

phased array of infrared-detector elements. The detector elements create a detailed 

temperature pattern called a thermogram, which is translated into electric impulses and then 

translated into data that can be displayed on the user screen. 

7.5.2 Types of Thermal Vision Equipment Available 

Thermal imagers are available in vehicle- or stationary-mounted, hand-held, or weapon-sight 

packages. Various models can provide general all-weather use under all light or no light 

conditions. Some imagers can perform well in fog, smoke, rain, or snow conditions. Thermal 

imagers have two ways of indicating the presence of intruders: “white hot” means that warmer 

objects in the picture are shown in white and “black hot” means that warmer objects are shown 

in black. 
7-7 

Sources of heat from objects that are not of interest to the user can be distracting and may 

result in the need for investigation and possibly response by members of the security 

organization. 

7.5.3 Characteristics and Applications 

Thermal imagers have the ability to operate successfully under many types of conditions in 

which other surveillance devices are of no value (e.g., all levels of light, smoke, fog, rain, or 

snow). One of the biggest advantages is that camouflage is not effective if used by adversaries 

to hide from thermal imagers. 

Thermal imagers can weigh several pounds, making them too heavy and cumbersome to carry 

for prolonged periods. Thermal imagers are more suited to permanent installations than 

temporary setup. The field of view that the device provides should also be evaluated and 

should be consistent and appropriate for the specific field application (e.g., thermal rifle optic 

should not be used for wide-ranging area surveillance as the field of view provided is small). 

Thermal imagers are susceptible to defeat through shielding the thermal signature of objects 

within the field of view. 

7.5.4 Testing 

Testing on a weekly basis and under different environmental conditions is recommended to 

ascertain that the device operates as advertised by the manufacturer. If the device is dropped, 

the user should test the device as soon as possible. 

7.5.5 Maintenance 

Most thermal imager devices require daily cleaning of the lens using a cleaner and soft cloth 

recommended by the manufacturer. Batteries should be routinely checked and replaced. 

7.6 Enhanced Night Vision (Fusion)

7.6.1 Principles of Operation 

Enhanced night vision (ENV) devices operate through the fusion of the I2 (Image Intensifier) 

tube and an infrared micro-bolometer, designed into a compact monocular design. The 

combination, via overlay, of these two technologies greatly expands the capabilities of a night 

vision or thermal imager device alone. 

7.6.2 Types of Enhanced Night Vision Equipment Available 

ENV devices are available as a hand-held observation tool or as a rifle optic. Some recent 

models allow the user to determine the percentage of night vision use and thermal imager use 

to enhance viewing capabilities under particular circumstances. (Refer to Figure 81.) 

Sources of heat from objects that are not of interest to the user can be distracting and may 

result in the need for investigation and possibly response by members of the security 

organization. 
7-8 

7.6.3 Characteristics and Applications 

This fusion technology, a combination of thermal imager and night vision technologies, has the 

ability to operate successfully under many adverse conditions, excelling in poor-visibility 

environments that would impede other devices. 

7.6.4 Installation Criteria 

Installers should follow the manufacturer’s recommendations. 

7.6.5 Testing 

Testing on a weekly basis and under different environmental conditions is recommended to 

ascertain that the device operates as advertised by the manufacturer. If the device is dropped, 

the user should test the device as soon as possible. 

 

Figure 81 These drawings illustrate the use of an enhanced night vision device, or fusion technology. The 

top left drawing shows such a device set for 100 percent I2

 (Image Intensification) use. The top right drawing 

shows it set for about 50 percent I2

 and 50 percent infrared use. The bottom drawing shows it set for 

100 percent infrared use. Obviously, different situations would require different settings to gain optimal 

information. 
7-9 

7.6.6 Maintenance 

Fusion devices require daily cleaning of the lens with a cleaner and soft cloth recommended by 

the manufacturer. Batteries should be routinely checked and replaced.

8-1 

8. ALARM COMMUNICATION AND DISPLAY 

8.1 Principles of Operation

8.1.1 Objectives and Goals of the Alarm Communication and Display System 

The primary objective of a physical security alarm system is to communicate alarm events 

received from sensors to a human operator. (Refer to Error! Reference source not 

found.Error! Reference source not found..) For a system to be effective, it must be capable 

of operating under all conditions and continuing to operate even when individual components or 

primary data communication paths fail, which is why redundant data communications 

capabilities are important. The goals of the system are to report alarms in a timely manner, 

never lose alarms, and survive any single-point failure with minimal or no degradation in system 

performance. 

8.2 General Guidance for Alarm Communication and Display Systems

In general, alarm communication and display (AC&D) systems should have the qualities 

described below: 

(1) A data communication subsystem should move alarm data in a timely manner. Alarms 

should be communicated to the alarm station operator within 2 seconds2

 of sensor 

activation, although less than 1 second is preferred. The data communication 

subsystem needs to be fast enough to allow the overall alarm system to meet these 

times. Alarm timing is measured starting at sensor activation and ending at alarm 

display (visual and audible) to the alarm station operator. 

(2) The data communication system should be robust with no single-point failures between 

field panels and the alarm stations. 

 Single-point failures are defined as the loss of the entire or a significant portion of 

the detection and assessment system capability through the loss of any single 

critical component/communications link.

 A critical component/communications link is one that, if failed, the detection 

and assessment capability of the security system would be completely or 

significantly degraded, thus requiring security force personnel to replace the 

functions of detection and assessment to maintain security system effectiveness. 

Intrusion detection and assessment systems should have no single 

component, link, or location that, if failed, would degrade the continued 

detection and assessment capability of the remainder of the system.

(3) The system should be designed with redundant data communication links. Redundancy 

is recommended between sensors and field panels. “Redundancy” refers to the ability of 

the system to complete the same task through multiple means. 

 

2 Two seconds is a standard time for many security applications. Refer to the section on alarm timing. 
8-2 

(4) The alarm system and associated data communications systems should not lose any 

intrusion or entry control alarms, events, tamper alarms, state-of-health messages, or 

any other alarm necessary to meet the level of protection of the system design. 

(5) The system should provide automatic notification to the alarm station operator when 

components of the intrusion detection and assessment system fail. This state-of-health 

monitoring should be continuous, with any faults being reported to the alarm station 

operators within 2 seconds, although a 1-second notification time is preferred. Also, the 

system should notify alarm station operators when components return to proper 

operation. 

(6) The data communication system should be highly reliable, with minimal downtime for 

repair. 

(7) The overall system should continue to operate in the event of a component failure 

caused by destruction or tampering at a single physical location. 

(8) The system should be designed to provide automatic “failover” to the greatest extent 

practicable, enabling continued detection and assessment when single components, 

communication links, or locations fail. “Failover” refers to the ability to switch to another 

resource if one component fails (e.g., the central processing unit, or CPU, for the central 

alarm station (CAS) fails over to the CPU for the secondary alarm station (SAS)). 

(9) Upon restoration of failed equipment or data communication links, the system should 

return to its original state within 30 seconds. No alarms should be lost while the system 

is returning to its original state. 

(10) Upon system restoration, the system should be capable of sustaining another failure at a 

single physical location and still maintain the capability to perform as designed. 

8.2.1 Line Supervision/External Connections 

In a high-security environment, all computer security networks are dedicated solely to security 

operations. The computer security network should not be connected to the Internet or other 

local or wide-area networks not related to security. When communicating between remote 

sites,3

 all data communications should be encrypted to the level corresponding to the sensitive 

unclassified or classified nature of the data communications. All system components should be 

protected against tampering and unauthorized manipulation. Detection, assessment, and 

access control devices that communicate using radiofrequency (RF) communications are not 

recommended for use in high-security applications as RF signals can be interrupted or jammed 

and thus inhibit equipment performance. 

In good alarm communication systems, failures of and tampering with critical components 

associated with alarm detection, transmission, and annunciation are continuously detected and 

reported as events to the alarm station console. (For timing issues, refer to Section 8.2.2.2, 

“Alarm Timing.”) The data communications system supports line supervision as detailed in 

Table 9. 

 

3

 Remote sites are sites that, because of their locati on, are not part of the int ernal d ata commu nications 

systems. For example, another location must use public lines because dedicated lines are not available. 
8-3 

To protect the system from unauthorized manipulation (e.g., hackers or others having 

malevolent intent), a security local area network (LAN), if used, should not be connected to any 

external computer network. The security system should operate on a stand-alone LAN that 

does not require connections to any external network. However, for associated entry control 

systems, the stand-alone system could allow (through firewalls and other information technology 

equipment) temporary or one-way connections to external networks to import badge information 

encrypted to the line supervision Class A standard. Detection, assessment, and access control 

devices that communicate using RF communications are not recommended for use in 

high-security applications as RF signals can be interrupted or jammed and thus inhibit 

equipment performance. System developers need to protect and secure communication 

equipment and media against unauthorized access. Equipment cabinets and field hardware 

containing electronic equipment or cable patch panels should employ tamper alarms to achieve 

this function. 

8.2.2 Alarm Handling 

8.2.2.1 Alarm Display Information 

Current AC&D systems use both text and graphic displays to uniquely identify alarms to an 

alarm station operator. Many types of information can be displayed, but some of the more 

important include the following: 

 Mode of any sensor. Mode refers to the status of a sensor. Is the device being 

monitored or ignored? Is the sensor on line or off line? Other standard terminology 

includes “access” or “bypass,” which means the same as “offline.” 

 Status or state of an event. Alarm status (state) can include alarming (detecting) or 

secure (no detection). 

 Time of events. 

 Location of events. 

At a minimum, the alarm station console should display the following information for alarm 

events: 

 Visual and audible annunciation of the alarm 

 Alarm type (intrusion, duress, tamper, etc.) 

 Alarm location 

 Time of alarm 

 Site-specific sensor identifier (a minimum of 64 characters is desirable) 

 Sensor state (alarm, secure, tamper) 

 Sensor mode (access, secure, offline) 
8-4 

Configuring the system to meet the needs of the site or facility is important. Flexibility is 

desired; for example, users should be able to configure the system to direct a particular alarm, 

tamper, or system event to the desired console. The system should be able to direct an event 

to more than one console (for example, sending all intrusion alarms to both the CAS and the 

SAS consoles). Administrators should be able to direct alarm events to consoles based on their 

location, priority, or sensor type. Figure 82 shows an example of an alarm station console 

display. 

Text and graphical displays need to be synchronized. Operations performed on a text display 

should, as needed, cause the graphics display to update. Operations initiated through the 

graphics display should, as needed, cause the text display to update. 

A good AC&D system needs synchronization of all internal “clocks” of all computers and 

subsystems to a single time base. It is recommended that the system utilize the network time 

protocol to perform this synchronization. System administrators should ensure that the system 

is synchronized and configured to display time as the security force requires (usually in the local 

time zone or universal time). 

8.2.2.2 Alarm Timing 

Intrusion detection system (IDS) alarms need to be timely so that alarm station operators can 

assess the alarms and dispatch response forces, as appropriate. In general, alarms, tampers, 

and system faults need to be annunciated in a timeframe that is a small fraction of the total 

response time. The IDS timing should be maintained at all times, regardless of other activities 

happening on the system. 

Console 

• Text 

Console

• Map(s) 

Assessment 

• Live video of the 

alarm site 

•

Surveillance 

• Live video as 

requested 

Surveillance 

• Live video as 

requested 

Automatic Automatic

Figure 82: An optimal arrangement of AC&D monitors. 
8-5 

“Time to report” is measured starting from the activation of the sensor, tamper, or component 

failure and ending when the alarm displays to a human operator in an alarm station. For most 

high-security system applications, alarms should be reported within 1 to 2 seconds of sensor 

activation. 

In malevolent or attack situations, many IDS alarms will be generated simultaneously. The 

system needs to handle malevolent situations without failing and without losing any of the 

multiple alarms. The system should be able to handle up to eight simultaneous alarms (i.e., 

eight alarms in 2 seconds) and should be able to count and display the number of 

unacknowledged alarms within 2 seconds of receipt of those alarms. The system should 

display the first alarm received and indicate the number of remaining alarms. In situations of 

multiple alarms, tampers, or system faults, the system should not fail or lose any alarm events. 

The system should be designed to handle an increased frequency of alarms and system event 

notifications, without prohibiting the alarm station operator from performing alarm 

acknowledgment activities on the console. When multiple alarms inundate the alarm console 

display, the number of unacknowledged system events, alarms, or tampers should not prohibit 

the proper display of subsequent events. 

8.2.2.3 Alarm Priorities 

Some IDS events, such as intrusion alarms and tamper alarms, are considered to be higher 

priority than other system events. In some cases, alarms received from specific intrusion 

sensors may be considered higher priority than others. The system administrator should assign 

priority levels to system events within the system, consistent with the site protective strategy 

and the objectives of the physical protection program. The system software should not make 

assumptions or place constraints on the priority assigned to a particular event. 

The system needs the ability to prioritize the display and handling of system events that include, 

but are not limited to: 

 Intrusion alarms from interior or exterior sensors 

 Equipment tampers 

 System faults 

 Data communication system faults, failures, or tampers 

 Alternating current power loss 

 Access control alarms and events 

 Low battery alarms 

 Duress alarms 

Prioritization of system events is a site-specific decision that should be made after consideration 

of the elements of the physical protection program, the site’s protective strategy, and the 

geography of the site. A good AC&D system should allow events to be assigned a priority 

based on location or event type, but exact priority assignments are site decisions. 

The system should automatically handle organization of incoming events. Normally, system 

events are displayed in order of priority and then by time of arrival. Administrators also need the 

capability to assign the same priority to different events (all alarms and tampers may have the 

same priority, for example). Also the system should allow alarm station operators the flexibility 

to handle any event out of priority order. 
8-6 

8.2.2.4 Alarm Logging and Reporting 

Alarm logging lets the system maintain a historical record of alarms so that alarm station 

operators, system administrators, or other authorized personnel can access a list or log of all 

system events and activity. The alarm control and display system should have the capability to 

export system log files into commonly used file formats for reporting or analysis. The alarm log 

should provide a record of all alarm events and all system events. 

Other useful information for the alarm log would include the following: 

 Time of operator acknowledgment 

 Time of operator cause assessment (completion of operator action) 

 A “tagging” ability so that the operator can tag an alarm event with its cause 

Using the log, the system should be capable of producing reports of alarm activity and providing 

the numbers and types of alarms based on their cause or location. The following are examples 

of reports that are beneficial in evaluating the continued health and maintenance needs of the 

system: 

 Nuisance and false alarm reports detailing the total number of alarms, false alarms and 

nuisance alarms (based on cause) per sensor zone (location), for a user-selectable time 

period. 

 Sensor grouping report based on type or location. In particular, reports are useful for 

interior sensors and exterior sensors. 

To avoid tampering by an insider, the system should prevent alarm station operators from 

deleting saved events. In addition, the system should be designed or programmed to ensure 

that an alarm station operator or system administrator cannot change the status of a detection 

point or deactivate a locking or access control device without the knowledge and concurrence of 

the alarm station operator in the other alarm station. 

The system can aid alarm station operators and administrators by having several automated 

features and capabilities. For example, good AC&D systems provide capabilities for logging 

events and saving them; then, when the log is full, the system should provide for an archive 

capability to save the information in a long-term storage medium. If the alarm reporting log or 

storage space (such as a hard disk) becomes filled to capacity, the system should not fail or 

lose information. A full system log should not cause the system to fail or degrade its 

performance. System capabilities may include the following: 

 Automatic notification (such as an e-mail to the administrator) when the log space 

becomes limited. The “Alarm Log Full” report can be generated at helpful intervals, such 

as 80 percent full, 90 percent full, and 95 percent full. Users can archive the log files 

before any information is lost or new information cannot be added. 

 An archive capability to move the log information to removable media, such as CDs or 

DVDs. 
8-7 

8.2.3 Closed Circuit Television Guidance 

Intrusion detection and assessment systems should interface with the alarm station console to 

provide automatic, integrated operation enabling a closed circuit television (CCTV) assessment 

system to automatically display video images in the area of the detected activity upon receipt of 

an alarm. The system should also enable manual switching of assessment assets in response 

to the alarm station operators’ commands in order to provide increased capabilities for 

assessment. 

When evaluating candidate systems, physical security analysts can use the following guidance 

to help determine the suitability of the CCTV system. The important elements that system 

purchasers or maintenance personnel may consider include the following: 

 The ability to display live video from any camera and the ability to record video from any 

camera. In addition to the automatic, integrated operation capability, the system should 

enable an alarm station operator to manually control the switching of camera displays. 

The system should automatically record video before the alarm event and upon receipt 

of an IDS alarm and should continue to record for a short time after the alarm is 

received, thus enabling video recall for further assessment. Also, the system should be 

capable of archiving past events on a removable medium. 

 A minimum equipment set, including four CCTV monitors, two primary assessment 

monitors (live and recorded), and two surveillance monitors for the operators to view 

video scenes generated by the site cameras. 

 Though a minimum equipment set is suggested, the system should be designed to 

accommodate the site-specific needs consistent with system configuration and overall 

size. 

8.2.3.1 Assessment Monitors 

Monitors dedicated for assessment are under the control of the AC&D system. These monitors 

play the live and recorded video from an alarm sector when the IDS detects activity within the 

zone of detection. If no alarm event is being handled, the monitors are either blank or show the 

highest priority unhandled alarm available to the AC&D system. 

The monitors are normally blank unless an alarm is being assessed or the alarm station 

operator has requested a particular view. When a view is selected by the operator, either for 

the purpose of alarm assessment or status determination, one of the primary CCTV monitors 

automatically displays live video coverage from the CCTV camera covering the area requested. 

If the view contains an alarm, the other primary monitor displays the alarm scene coverage that 

was recorded automatically on the recorder when the alarm occurred. In most cases, recorded 

alarm video is “looped” to repeatedly show the few seconds of video before and after the alarm 

event. If the scene does not contain an alarm, no recorded view is present. 

The following scenario describes how a system could automatically process alarm video with 

involvement from an operator: 
8-8 

(1) When two or more alarms are awaiting assessment, the monitors should show the 

highest priority live and recorded video scenes, unless the alarm station operator has 

chosen to view a lower priority alarm. Upon completion of an assessment by the alarm 

station operator, the system should automatically display the highest priority remaining 

alarm’s video (live and recorded). 

(2) At all other times these monitors may be blank. The system should not replace the 

primary monitor scenes until the operator either ends the assessment or selects a new 

alarm. 

(3) Alarm station operators may view specific alarm sector video by selecting appropriate 

sectors or sensors on the AC&D console. The AC&D system then displays the live 

video for that sector. Thus, the assessment monitors are under control of the AC&D 

system, while the AC&D system is under the control of the alarm station operator. 

(4) In some instances two additional assessment monitors might be required for alarm 

zones that use two video cameras for full video coverage of the zone. In most cases, 

however, a proper sector design requires only a single camera for assessment. 

8.2.3.2 Surveillance Monitors 

The free monitors that are not primary alarm assessment monitors should be available to the 

alarm station operator for surveillance purposes. Alarm station operators should have the 

capability to assign a camera from any camera view to show live scenes on these surveillance 

monitors at any time. If one of these monitors is showing a scene in which an alarm occurs, the 

live scene coverage for the alarming sector will be duplicated; the live scenes will be displayed 

on the free monitor and on the assessment monitor. These monitors are under the control of 

the operator and not the AC&D system. 

8.2.3.3 Prealarm and Postalarm Video 

In addition to live presentations, the system should interface with a video recording subsystem 

to provide a record of alarm events and allow alarm station operators to replay the camera 

images from the alarm. Recording capabilities should be automated and actuated by alarm 

signals. The alarm station console can be the main place to control the video recording system. 

The system needs to record image frames at a sufficient speed to capture the cause of the 

alarm. Display monitors need the capability to view both the current live camera information 

and the recorded information. 

Within the recorded video frame(s), the time, date, and location need to be embedded and 

displayed in the image for current and future reference. 

For assessment video recording, video should be recorded several seconds before and several 

seconds after (pre- and post-alarm video) an alarm event. A good general range of pre- and 

post-alarm video clips is 3 to 10 seconds, with about 5 seconds being optimal. The AC&D 

system and associated video recording systems should allow pre- and post-alarm clip recording 

times to be adjusted for site conditions. 

The alarm station operator needs the ability to display any camera image to a surveillance video 

monitor at any time. Even if new alarms are occurring, any video being displayed on the 

assessment monitors should not be removed from the monitor unless commanded by the alarm 
8-9 

station operator. However, CCTV systems need the capability to alert the operator or to call the 

operator’s attention to an alarm displayed on a video recorder/monitor. The system should not 

constrain the operator; for example, the operator may need to select video information 

associated with another incident out of priority order. 

CCTV systems should detect and report tampering and loss of video signals. 

8.3 Types of Alarm Communication and Display Systems Available

A variety of manufacturers produce AC&D systems. The systems rely on commercial, off-theshelf computers and network components but are customized through proprietary software 

created by the manufacturer. When investigating potential vendors of AC&D systems, security 

analysts should have already defined their needs for the specific facility. In addition, security 

requirements and specifications for the AC&D system should be defined in advance to assist in 

evaluating vendors’ offerings. 

8.4 Sources of Nuisance Alarms

The AC&D system is not a significant source of nuisance alarms. Low-probability 

communications faults have been known to introduce nuisance events, but recent changes to 

the communications equipment used in alarm systems has greatly reduced even this low 

probability. Remote power sources (e.g., those at field panels) can cause nuisance alarms. 

The primary source of nuisance alarms comes from sensors and not from the AC&D system. 

8.5 Installation Criteria

AC&D systems are somewhat different than sensors in that limited, specific criteria apply to all 

possible systems. One criterion for the installation of an AC&D system and its communications 

and power is that these systems must be installed in accordance with the National Electrical 

Code as is the case with many industrial electrical components. 

In general, AC&D vendors have either specific installation criteria or instructions that must be 

followed. Many vendors allow only fully trained and qualified distributors to install their systems. 

For other systems, a team of properly trained engineering and technical personnel will be 

necessary to correctly install a complex AC&D system. AC&D vendors are the best source of 

information on the criteria necessary for installing their systems. 

8.6 Testing

8.6.1 Failover Testing 

The system will occasionally fail because of power outages or component failure. Failover 

testing involves the ability to simulate these power or mechanical failures and then check the 

system to ensure that it responds accurately to system failures. Failover testing involves the 

following actions: 

 Identifying all critical components through the use of fault tree analysis (refer to 

Figure 85) or similar techniques. The fault tree allows analysts to explore all the 

components of a system and define all the events (single or in combinations) that could 

cause a system failure. Using standard logic symbols (Figure 84), analysts build system 
8-10 

maps to show all the undesired system states and the components that could contribute 

to a system failure. The fault tree analysis technique has been used in safety and risk 

engineering for the determination of safety hazards. 

 Identifying failure causes for all components discovered during fault tree analysis 

(e.g., servers, workstations, switchers, routers, other data communications devices, and 

power sources). 

 Causing failures in various components of a system. 

 Verifying that the system continues to communicate data and display alarm information 

before, during, and after the failure. 

 Verifying that the system restores to its original state once the failure is removed and 

that alarms continue to be captured, communicated, and displayed during the 

restoration.

 

Figure 83: Fault trees allow analysts to map events and their potential causes. (Refer to the next figure for 

explanations of symbols.) 
8-11 

Figure 84: Symbols used in the graphical representation of a fault tree. 

8.6.2 Acceptance Testing 

Acceptance testing is typically performed at installation and verifies that the system meets all 

specifications. Acceptance testing typically consists of tests that challenge and demonstrate the 

performance criteria associated with the manufacturer’s specifications. Acceptance tests should 

be conducted anytime the system software changes or major hardware additions are installed. 

8.6.3 Operability Testing 

Operability tests should be conducted during the normal operation of the system. In most cases 

AC&D operability can be tested by performing sensor and video operability tests and observing 

that generated events are displayed properly on the AC&D console.4

 

Table 9 shows an example of AC&D operability testing. 

8.6.4 Performance Testing 

Performance testing of the AC&D system is typically done as part of the acceptance test 

process. Those requirements that have a measurable performance metric are tested 

appropriately (timing tests, for example, are measured with external time measurement 

devices). In general, the AC&D system performance changes only when hardware or software 

changes are made. There is little degradation or component drift associated with a good AC&D 

system. This is a distinct difference between the AC&D system and its associated sensors. A 

semi-annual performance test is recommended. A performance test should also be conducted 

after major hardware or software installations. 

 

4

 Many sites c onduct o ngoing oper ability tes ts ( weekly or monthly) thr oughout the year on a sc hedule that 

ensures that all alarm points are covered at least once per year. Other effective schedules are possible. 
8-12 

Table 9: Operations Testing Matrix 

Required Feature Test To Ensure Operability 

Time, date, and location are embedded 

in the image of the recorded video. 

Alarm station operator inspects console display of the 

recorded video for the time, date, and location. 

Video should be recorded several 

seconds before and several seconds 

after (pre- and post-alarm video) an 

alarm event. 

While an alarm station operator works at the console, 

a security officer should perform a test of the IDS at 

the desired location. The alarm station operator 

inspects console display of the recorded video for the 

site-specified number of seconds for pre- and 

post-alarm video. 

Display any camera image to a 

surveillance video monitor at any time. 

Alarm station operator ensures that all cameras 

respond to commands to display on the system in the 

order chosen by the operator. 

CCTV systems should detect and 

report tampering and loss of video 

signals. 

While an alarm station operator works at the console, 

a security officer should perform an intentional tamper 

with the CCTV apparatus to cause an alarm at the 

console. To test for loss of video signals, the security 

officer in the field should turn off the camera to ensure 

that the alarm station operator receives a system 

notification of the signal loss. 

8.7 Maintenance

A strong, proactive maintenance program should be in place to maintain the AC&D subsystem. 

Manufacturers of AC&D systems have specific recommendations on the maintenance 

requirements. The appropriate maintenance personnel should be on site or on call to meet 

required “mean time to repair” requirements specified by the vendors or be available to meet the 

site-specific requirements, which may vary depending on the environmental conditions at the 

site. 
9-1 

9. EMERGENCY AND BACKUP POWER 

9.1 Principles of Operation

The primary power source for critical security systems and components for a limited area should 

come directly from the normal onsite power distribution system or directly from the public utility. 

Because of the potential for a loss of power, whether caused by a natural phenomenon such as 

weather or by a malicious act committed by an adversary, a facility should have reliable backup 

and/or emergency power sources on site that will provide power when needed. 

All critical security systems and components, including the following, should have an 

emergency/backup power capability in case of the loss of primary power if they are required to 

function as intended to maintain a high physical protection standard: 

 Intrusion detection equipment 

 Assessment equipment (closed circuit television systems) 

 Illumination equipment (lights required for assessment cameras) 

 Autom ated access control systems 

 Alarm monitoring systems 

 Nonportable communications equipment 

These power sources should contain an automatic switching capability to the auxiliary source of 

power (battery and/or generator) that will function immediately without causing false alarms and 

without causing a loss of security system function or data. (See Figure 85.) 

Figure 85: A facility must have emergency and/or backup power supplies so that in the event of a loss of 

power, critical parts of the security system will continue to operate without loss of key information or 

functionality. 
9-2 

It is important that the alarm stations be designed such that they will automatically receive an 

alarm indicating any of the following conditions: 

 The primary power source has failed. 

 The facility has transferred to an emergency/backup power source. 

 The emergency/backup power source has failed. 

In the design and selection of an emergency/backup power source, consideration should be 

given to site-specific conditions for the capability to restore primary power. The capability of the 

emergency/backup power source to sustain security system operations should be based on the 

timeframe to restore primary power as derived through a site specific analysis. 

9.2 Types of Emergency and Backup Power Supplies

While a wide variety of emergency/backup power mechanisms are available, the three primary 

categories that are used by most facilities are the following: 

 Uninterruptible power supplies (UPSs) 

 Batteries 

 Engine generators (EGs) 

9.2.1 Uninterruptible Power Supplies 

UPSs are typically used to supply an uninterrupted source of power to important instrumentation 

and control systems enabling continuous operation during the loss of normal power without loss 

of system or component functionality. They are also used to provide continuous, quality power 

for systems sensitive to disturbances occurring in an electrical power distribution system caused 

by switching, faults, or power transfer. UPS designs may include various combinations of 

batteries, rectifier/charger, battery transfer, bypass switch, and inverter. Most UPS systems are 

placed between the primary power source and the component it protects, effectively funneling 

all power at all times while keeping its own batteries charged. 

9.2.2 Battery Systems 

A battery system includes all switchgear and distribution equipment necessary to provide quality 

voltage and current as required by the connected load. The batteries are normally in full float 

operation where they are connected in parallel with a charger and the load, and where the 

charger supplies the normal direct current (dc) load plus any self-discharge or charging current, 

or both, required by the battery. 

9.2.3 Engine Generators 

An EG is a device that converts mechanical energy to electrical energy, generally by using 

electromagnetic induction. For most industrial applications, a diesel engine supplies the 

mechanical energy. An EG, when properly sized and designed, will provide reliable electrical 

power to the intended load equipment for the required amount of time. 
9-3 

9.3 Installation Criteria

Directions and recommendations provided by the manufacturer should be followed as 

appropriate. Emergency/backup power systems and key components, including batteries, EGs, 

fuel tanks, and switch gear, should be physically located where they will be protected; they 

should either be under continual surveillance or contained in a locked enclosure with an 

intrusion detection system installed to protect against tampering and unauthorized access. 

Nonrechargeable batteries should be replaced whenever their voltage drops 20 percent below 

the rated voltage or based on the manufacturer’s recommendation. An alarm signal should alert 

the alarm stations of this condition. 

An EG must be capable of providing power compatible with the equipment it sources. The EG 

should have adequate capacity and rating for all loads to be operated simultaneously. The 

emergency/backup power system should start automatically (or be brought on line) upon loss of 

primary power. The transfer of power from battery to EG power should occur at a set point 

before the battery power declines in voltage below the levels needed to continue the operation 

of assigned equipment. This transfer is typically set to occur prior to battery voltage falling 

below 80 to 90 percent of normal in the event the generator initially fails to start. 

9.4 Testing

A regular program of testing emergency/backup power sources is a key to keeping them in 

optimal operating order. Three types of testing need to be performed at different times in the life 

of a power system: acceptance testing, performance testing, and operability testing. 

9.4.1 Acceptance Testing 

Acceptance testing is the process that a site must go through after an installer has completed 

the installation of the system but before the system is used operationally. 

Acceptance testing consists of two parts: 

(1) The newly installed components should be thoroughly inspected to ensure that the 

system has been installed according to manufacturer’s specifications and the detailed 

engineering drawings for the site-specific design/installation. A facilities engineer will 

need to ascertain that commonly accepted practices for electrical, mechanical, and 

plumbing work have been followed, including safety requirements. 

(2) A complete and positive performance test should be performed (see next section). 

9.4.2 Performance Testing 

Performance testing is the periodic test of the full range of expected capabilities of a particular 

emergency/backup power system. Most important, the emergency/backup power system 

should be demonstrated to fulfill the following purposes: 

 The system receives instant notification when primary power has failed. 

 The system becomes fully operational within the timeframe for which it was designed. 

 The system provides the power voltage for which it was designed. 
9-4 

 The system continues to operate for the length of time for which it was designed. 

 The system can reliably return to normal power when appropriate. 

This complete test should be accomplished at least once every 12 to 18 months, or whenever 

there has been a change to the system, including the rerouting of power sources, movement of 

equipment, or an upgrade of features or components. 

9.4.2.1 Engine Generator Testing 

An integrated system test should be performed at least once a year to demonstrate proper 

operation during a loss of primary power. This series of tests demonstrates the ability of the EG 

unit and associated switch gear to perform their intended function under simulated accident 

conditions. In addition to the steps performed during the monthly test outlined in the next 

section, perform the following steps should be performed: 

(1) Verify that the buses that will be powered by the EG deenergize and loads shed, as 

required. 

(2) Verify that the EG starts automatically and attains voltage and frequency within 

prescribed limits and time. 

(3) Verify the proper loading sequence and that voltage and frequency are within the 

manufacturer’s specifications for connected loads for both transient and steady-state 

conditions.

(4) Run the EG for at least 8 hours after temperature equilibrium is reached.

(5) Demonstrate that the EG operates at its continuous rating and, if installation permits, 

efficiency rating (also called the load power factor). If the connected load is above the 

continuous rating but within the short-time rating, the unit should be operated at the 

short-time overload value for no longer than the time specified for the short-time rating.

(6) After the test is complete, shut the unit down and within 5 minutes demonstrate the 

ability of the unit to perform a hot restart and load to its continuous rating. 

9.4.2.2 Uninterruptible Power Supply Testing 

A UPS in its standby or normal operating mode may not demonstrate many of the various 

features that may be required to function during emergency conditions, which include, but are 

not limited to, a loss-of-power or equipment failure. 

The tests outlined below are recommended UPS tests and, depending on the design of the UPS 

system, should be performed according to manufacturer’s recommendations or on at least an 

18-month interval: 

 Light-Load Test—Operate controls and instruments for stability and values of voltage 

and frequency. 

 Synchronization Test—Measure the rate of frequency change during synchronization 

and UPS voltage during transfer (when an alternate source is part of the design). 
9-5 

 Alternating Current Input Failure Test—Verify that transfer to dc source occurs as 

designed. 

 Alternating Current Input Return Test—Verify that system performs stable return to 

normal source. 

 Transfer Test—Forward and reverse (UPS systems using static bypass switches). 

 Rated Full-Load Test—Check that system meets connected or rated load-carrying 

capability for the required duration for extremes of alternating current (ac) and dc input 

voltage. 

 Output-Voltage Balance Test—Measure phase angle and voltage to meet specifications 

for balanced and unbalanced conditions. 

 Harmonic-Components Test—Measure harmonic content in the output voltage for linear 

and nonlinear load conditions. 

9.4.2.3 Testing Batteries 

The only real measure of a battery’s capacity and capability to provide power to its required load 

is derived from the performance of two different tests: the performance discharge test and the 

service test. During the performance of these tests, the battery will be unavailable for duty 

because of significant discharge. These tests should be performed only under conditions when 

the unavailability of the battery is acceptable, or provisions should be made (compensatory 

measures) for an alternate source to be temporarily connected to the loads for the duration of 

the test and recharging of the battery. 

The performance discharge test indicates the remaining capacity of the battery expressed as a 

percent of the rated capacity. This provides an indication of the remaining useful life of the 

battery. 

The service test demonstrates the ability of the battery to carry its required load for the required 

time period. To perform the service test, the load profile for the battery must be known. 

9.4.3 Operational Testing 

Operational testing is the monthly testing of an emergency/backup power system to confirm that 

it is functional. Because regular maintenance is critical in many systems, it is highly 

recommended that this operational testing requirement be performed at the same time as 

regular maintenance. Because it is sometimes difficult to distinguish between what constitutes 

periodic testing and what constitutes periodic maintenance, the two have been combined in 

Section 9.5, “Maintenance.” 

Table 10 (taken from DOE-STD-3003-2000) provides an example of good practices for 

surveillance and testing of lead-acid cells, including expected values and testing frequency. 

Adjustments (increases or decreases) to the intervals in the table should be based on 

experience and manufacturer’s recommendations. 
9-6 

Table 10: Typical Lead-Acid Battery/Cell Surveillance and Tests

Subject (Note 3) Values (Note 1) Period 

 

Battery Terminal Voltage (typical 60-cell 

battery) 

(129–130.2) volts PbSb 

(130.2–135) volts PbCa 

Monthly 

 

Electrolyte Level Between fill lines (distilled 

water only) 

Monthly 

 

Cell Float Voltage 

(Pilot Cell) 

(2.15–2.17) volts PbSb 

(2.17–2.25) volts PbCa 

Monthly 

 

Cell Float Voltage 

(All Cells) 

(2.15–2.17) volts PbSb 

(2.17–2.25) volts PbCa 

Quarterly 

 

Specific Gravity (Pilot Cell) 1.215 ± 0.010 Monthly 

Specific Gravity (All Cells) 1.215 ± 0.010 Quarterly 

Cleanliness and Corrosion Check (Note 2) Monthly 

Resistance Measurement Cell to Cell and 

Terminal Connections 

< 20% above the value 

when new or after cleaning 

or retorquing bolts 

Yearly 

 

Battery Capacity Test (Performance 

Discharge Test) 

> 80% of capacity (Note 5) 5 years 

 

Battery Load Test (Service Test) Design load and duration 

with adequate voltage 

Yearly (Note 4) 

Note 1 Values outside these ranges indicate that action is necessary to restore the 

parameter to within the specified values. 

Note 2 Battery cleaning should be done with baking soda and water with clear water 

rinse—no other cleaning materials should be used. 

Note 3 All manufacturer’s safety precautions should be observed when working on 

batteries. 

Note 4 Not required where battery is for engine generator only and not other loads. 

The periodic monthly start of the engine generator is a load test. Load tests 

should be done in as-found condition. 

Note 5 Battery capacity (performance discharge) test is used as a battery age 

indicator. Initially, a battery should be fully charged, temperature near 25°C, 

and terminals clean. 
9-7 

9.5 Maintenance

Because of the nature of emergency/backup power supplies, as well as their expected irregular 

schedule of use, regular maintenance is critical to guaranteeing their full functionality and 

reliability when called upon when the primary power source is unavailable. 

9.5.1 Engine Generators 

To avoid unnecessary and premature degradation of the EG, the manufacturer’s 

recommendations should be followed in regard to prelubrication, acceleration, loading, and 

unloading. All engine starts, for testing purposes, should follow the manufacturer’s 

recommendations for prelubrication and/or other warmup procedures to minimize mechanical 

stress and wear.

Regular exercising of the EG keeps engine parts lubricated, prevents oxidation of electrical 

contacts, uses up fuel before it deteriorates, and in general, helps provide reliable engine 

starting. The generator set should be run at least once a month for a minimum of 1 hour loaded 

to no less than one-third of the nameplate rating. 

The following, at a minimum, should be performed at least once per month, unless otherwise 

specified by the manufacturer: 

 Record the as-found condition and the identity of the test personnel. 

 Verify that the EG starts on a simulated loss of offsite power and accelerates to 

operating rpm in (the required value) seconds. Generator voltage and frequency should 

be (required value + 10 percent) volts and (60 + 2 percent) hertz within (required value) 

seconds. 

 Verify that the starting system disengages properly. 

 Verify that fuel tank levels (fuel storage tank, day tank, and engine tank) are within 

specifications. 

 Remove accumulated water from fuel tanks and oil/water separator. 

 Verify that the fuel transfer pump system starts and that fuel is being transferred from the 

storage tank to the day and engine-mounted tank (if present). 

 Verify that the EG can accept loads up to 90 percent of the continuous rating for the 

duration of the test (time should consider the manufacturer’s recommendations). This 

may be done using normal loads or a load bank, or by synchronizing to the offsite grid if 

this capability is available. If a load bank is routinely used, a dedicated connection 

should be provided. The value of 90 percent is used to provide margin to avoid 

inadvertent overloading. 

 Verify the cooling water tank level. 

When recording test results, a failure should be recorded if the EG fails to start, accelerate, 

reach nominal voltage and frequency, or accept the rated load within and for the time required, 

or if it otherwise fails to satisfy the specified acceptance criteria.
9-8 

9.5.2 Uninterruptible Power Supplies 

The UPS system should be inspected and tested on a frequent basis according to the 

manufacturer’s recommendations. The frequency of the inspections is dictated by the type of 

service to which the equipment is subjected (e.g., duty cycle, chemicals, dust and heat) and 

trending. Less frequent activities such as internal cleaning, filter replacement, checking 

electrical connections for tightness, and calibration of instruments should be done according to 

the manufacturer’s recommendations. 

9.5.3 Batteries 

Many types of batteries, if allowed to sit without a charger, will internally discharge, often with 

irreversible cell degradation. For these types of batteries, it is important to maintain proper 

charging float voltage during standby. Because of inherent differences between cells, float 

voltage and specific gravity values will vary from cell to cell over time. If cell float voltages 

and/or specific gravity values are allowed to remain in an unequal condition for extended 

periods of time, cell sulfation will result. To overcome this problem, a periodic equalizing charge 

must be applied to equalize cell voltages and specific gravities. The manufacturer’s 

recommendations should be followed in regard to equalizing charge. When performing an 

equalizing charge, care should be taken to ensure that the charger voltage does not exceed the 

voltage rating of the load connected during the equalize charge. Batteries are usually rated at a 

temperature of 25 degrees Celsius. Higher temperatures will improve capacity at high 

discharge rates but significantly reduce battery life. Lower temperatures have a significant 

effect in reducing battery capacity. Typical battery types for standby service are lead-acid 

(calcium (Ca), antimony (Sb)), pure lead (Pb) (generally a “round cell”), or nickel-cadmium 

(NiCd). Manufacturers will provide necessary information on the care, precautions, charging, 

and treatment of specific batteries including maintenance during periods of storage.