NBSIR 73-271 (l?)

Field Service Test Model:

Computer-Controlled U System

Manual for System

R. J. Carpenter

E lectronic Instrumentation

Measurement Engineering

Institute for Applied Technology

K. M. Gray

D. S. Grubb

L. J. Palombo

Measurements Automation

Information Processing Technology

Institute for Computer Sciences

and Technology

August 23. 1973

Instruction Manual

Prepared for Department of the Air Force HQ USAF (AFTAC TAP)

Patrick A. F. B.. Florida 32925

NBSIR 73-271

FIELD SERVICE TEST MODEL:

COMPUTER-CONTROLLED U SYSTEM

MANUAL FOR SYSTEM

R. J. Carpenter

Electronic Instrumentation

Measurement Engineering

Institute for Applied Technology

K. M. Gray

D. S. Grubb

L. J. Palombo

Measurements Automation

Information Processing Technology

Institute for Computer Sciences

and Technology

August 23. 1973

Instruction Manual

Prepared for Department of the Air Force

HQ - USAF (AFTAC TAP)

Patrick A. F. B.. Florida 32925

'<"»fAU 0*

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

FIELD SERVICE TEST MODEL: COMPUTER-CONTROLLED U SYSTEM

MANUAL FOR SYSTEM

by

R. J. Carpenter, K. M. Gray

D. S. Grubb and L. J. Palombo

INTRODUCTION

The Field Service Test Model uses a computer to control the

operation of from 1 to 15 EECO 881 receivers for unattended operation. Each receiver is connected to the computer by an ADACS

(Automatic Data Acquisition Control System) Interface Chassis, which

provides the necessary decoding and conversion for communication

between the receiver and the computer (see figure 1).

This manual describes the operation of the overall system.

GENERAL DESCRIPTION

The purpose of the receivers is to produce a record of the

phase of several VLF radio signals over a long period of time. As

originally used, each receiver was run independently with its own

output recording device and with some operator monitoring of the

receiver controls.

The computer-controlled U system uses a small computer to

monitor the status of the receiver and its output signal; perform

the necessary programmed calculations on the status and signal;

manipulate the receiver's controls for proper operation of the

Certain commercial equipment and materials are identified in

this paper in order to adequately specify the components used. In no case does such identification imply recommendation or endorsement

by the National Bureau of Standards, nor does it imply that the

material or equipment identified is necessarily the best available

for the purpose.
receiver; and record the phase of the output signal.

The system consists of a minicomputer with a 16-bit word size

and 32K words of core memory, several computer peripheral devices

(teletypewriters, etc.), an analog subsystem for receiving analog

signals from the receivers, a digital subsystem for digital signals

to and from the computer, a connector panel, and up to 15

receivers with their attached ADACS Interface Chassis units

(see figure 1)

.

The receiver functions that must be computer-controlled for

proper operation of the receivers in unattended usage are: RF

gain, uncorrected phase, tracking rate, and blanking level. See

figure 2.

2.1 RF GAIN

In manual operation, the RF gain is set by the operator, using

the RF Gain control on the front panel of the receiver. In automatic (computer-controlled) operation, the computer controls the RF

Gain by monitoring the amplitude of the receiver's output signal

and by sending the appropriate gain level information back to the

receiver. (The RF Gain control on the front panel of the receiver

is deactivated when the receiver is in automatic operation.)

The amplitude is converted into binary bits by the analog

subsystem of the computer. The computer specifies the gain level

in the form of 5 binary bits. These bits at decoded into 14 lines

by the ADACS unit for the operation of relays in the receiver,

which select the resistance to be used in the receiver's RF gain

circuit

.

2
2 . 2 PHASE

In automatic operation, the computer monitors the difference

between the corrected and uncorrected phase signals of the receiver

to determine when to order a phase shift of the uncorrected phase

signal. The phase difference is converted into binary bits in the

analog subsystem of the computer. When a phase shift is needed,

the computer sets the Phase Change bit (15) and generates an output

transfer. Each output transfer is accompanied by a flag, which is

a 10-microsecond pulse. The Phase Change bit and the flag pulse

are used by the circuitry in the ADACS unit to generate a 10-microsecond Phase Change Pulse, which is sent to the receiver to shift

the uncorrected phase signal 50 microseconds.

2.3 TRACKING RATE

In manual operation, the tracking rate of the receiver is

adjusted using the Tracking Rate switch on the front panel of the

receiver. In automatic operation, the computer uses the peak-topeak noise (phase variation) on the phase output of the receiver

to determine the tracking rate for the receiver.

The computer specifies the tracking rate in the form of 4

binary bits. These bits are decoded into 6 lines by the ADACS unit

for the operation of relays in the receiver, which select the

receiver's tracking rate.

3
,4 BLANKING LEVEL

In manual operation, the Blanking Level control on the front

panel of the receiver is set by the operator. In automatic operation, the computer monitors the blanking pulses from the receiver

to determine the blanking level for the receiver. (The Blanking

Level control on the front panel of the receiver is deactivated

when the receiver is in automatic operation.)

The blanking pulses from the receiver are converted into an

analog voltage level by circuitry in the ADACS unit. The voltage

is called Blanking Percentage and it is converted into binary bits

by the analog subsystem of the computer. The computer specifies

the blanking in the form of 6 binary bits. These bits are converted into an analog blanking level voltage by the ADACS unit for

use by the receiver.

5 FREQUENCY

The frequency of the receiver is always determined by the

setting of the Channel Select switches on the front panel of the

receiver. The setting of the switches is monitored by the computer.

6 OPERATIONAL STATUS

A change in the operational status of a receiver will cause

a computer interrupt. Since a single interrupt line is shared by

all of the receivers, when the computer receives an interrupt it

must examine the status lines for each of the receivers to determine

which has changed its status. The status lines are for INE (Invalid

Data Equipment sensed), Manual/Automatic switch, and Maintenance/

Normal switch.
2.7 MANUAL/AUTOMATIC SWITCH

The Manual/Automatic switch is on the front panel of the ADACS

Interface Chassis. Its output is used by both the receiver and the

computer.

2.8 MAINTENANCE/ NORMAL SWITCH

The Maintenance/Normal switch is on the front panel of the ADACS

Interface Chassis. Its output is used only by the computer (as a

status indicator)

.

2.9 CARDIOID

The three binary bits from the cardioid are monitored by the

computer. A change in the least significant bit will cause an

interrupt to the computer, which will then examine the status of

digital input word that contains the three bits.

3. SYSTEM COMPONENTS

The system components consist of the computer subsystem; the

real-time clock; the a-c power loss detector; the missing pulse

detector; the receivers and ADACS Interface Chassis units; and the

Test Unit. All except the Test Unit are shown in figure 1.

3.1 COMPUTER SUBSYSTEM

The computer subsystem consists of the CPU (central processing

unit), the computer peripherals (teletypewriters, paper tape reader,

etc.), the analog subsystem, the digital subsystem, and the connector panel.

The computer subsytem is described in the Manual for Computer

Subsystem. The computer is a general-purpose digital computer with

a 16-bit word size and 32 K words of core memory.
2 REAL-TIME CLOCK

A real-time clock is attached to the system via the digital

portion of the Connector Panel. The clock uses a Cesium beam

standard and may be set to an accuracy of one microsecond. It

generates an interrupt to the computer every second and every

minute. As used with this system, it provides time information in

days, hours, minutes, and seconds (see figures 8 and 9).

3 A-C POWER LOSS DETECTOR

The power loss detector is shown in figure 10. It is used to

alert the operator in the event of a power failure.

4 MISSING PULSE DETECTOR

The missing pulse detector (figure 11) is used to detect the

condition that exists when the computer, due to a programming error

or computer malfunction, is locked in a program loop. Since the

computer program is no longer controlling the system when it is in

this state, an external detector is needed to return the receivers

to manual operation.

The missing pulse detector circuit receives a 10-microsecond

pulse from the computer at least once every 20 seconds from the flag

bit (the pulse generated on all digital output transfers) . As long

as these pulses occur, the retriggerable one shot circuit, NE555,

will be on. The output of the NE555 circuit is used by the optical isolator circuit, TI 112, to provide the gate voltage for the

SCR (silicon-controlled rectifier), which completes the circuit to

the relay. When the relay is energized, it connects the input

power to the ADACS units.

6
If the computer becomes locked in a program loop, it will no

longer be generating output pulses. Without these pulses, the NE555

circuit will time out and drop its output to the optical isolator.

Without its input, the optical isolator will no longer provide the

gate voltage for the SCR, and the SCR will open the circuit to the

relay. When the relay circuit is opened, the relay contacts will

disconnect the power to the ADACS units. The loss of power to the

ADACS units will cause the Manual/Automatic relays in the various

receivers to drop to the Manual position, thereby forcing the

receivers into the manual mode of operation.

5 RECEIVERS AND ADACS INTERFACE CHASSIS UNITS

The receivers and ADACS units are described in the Manual for

Receiver and ADACS Interface Chassis. Up to 15 receivers may be

attached to the system.

6 TEST UNIT

The Test Unit is not a part of the operational system, but is

used for maintenance of the receiver and ADACS units. The Test Unit

is described in the Manual for Test Unit.

SYSTEM INTERFACES

The interfaces between the component units of the system are

shown in figure 1. Interfaces within the computer subsystem are

shown in the Manual for Computer Subsystem and are covered in detail

in the manuals supplied by the computer manufacturer. The interfaces between the receiver, the ADACS Interface Chassis unit, and the

Connector Panel are shown in more detail in figure 2. The unit/

detachment input is merely a connector wired to denote the appro-
priate number.

1 CABLING AND PIN ASSIGNMENTS

The cable connections for the system are shown in figures 3 and

4. The receiver and the ADACS Interface Chassis are interconnected

as shown in figure 3. The dotted lines within the box for the ADACS

unit show relationships between inputs and outputs. The interrupt

lines are "daisy-chained" from unit to unit, so that only a single

line is sent to the Connector Panel.

The assignment of cable connectors on the Connector Panel to

the various receivers and other units is shown in figure 4. The LSB

(least significant bit) of the cardioid information from each ADACS

unit (pin number P in the cable) is wired to the Common Alarm card

(1191) of the computer subsystem's I/O Digital Interface (1100).

The output of the alarm is wired to interrupt number 8.

Pin assignments for the various cables are shown in figures 5

through 9.

2 ELECTRICAL

The digital signals of the system all use TTL levels. A

logical "one" is nominally plus 5 volts and a logical "zero" is at

ground

.

There are three types of analog signals used between units of

the system: phase difference, amplitude, and blanking percentage.

The phase difference signal has a voltage range of from zero to

plus 10 volts. The amplitude signal has a voltage range of from

zero to plus 7.816 volts. The blanking percentage signal has a

voltage range of from zero to plus 10 volts.

8
4.3 MECHANICAL

The connector part numbers and other mechanical details are

covered in the manuals on the associated units. The construction

of cables using BNC connectors is common to the system and is

shown in figure 12. The construction of cables using multi-pin

connectors is also common to the system and is shown in figure 13.

5. COMPUTER WORD ASSIGNMENTS

The digital inputs to the Connector Panel (frequency, cardioid,

INE, and the switch settings in the ADACS unit) are formed into a

word for the computer. This is shown in figure 5.

The digital outputs from the Connector Panel (tracking rate,

RF gain, blanking level and phase) are generated from a computer

word, which is shown in figure 6.

The analog inputs to the Connector Panel (phase difference,

amplitude and blanking percentage) are each used (in turn) as the

input to the analog-to-digital converter in the analog interface to

generate digital bits, which are formed into a word for the computer.

The bits are arranged with the least significant bit from the

converter as bit 15 and the remaining bits in order of increasing

significance.

The real-time clock provides time information in terms of day,

hour, minute and second. The two words are shown in figures 8 and

9.

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j U.S. DEPT. of comm. 1. \>{ 1-!!'. A i ' Iv > N i >K K i\ ; NO. BIBLIOGRAPHIC DATA

SHEET NBSIR 73-271

...... .......... 3. Recipient's Accession No.

, — 1 A T*'I * I

* I I" ( \:i i v 1 ; Lj 71 '1' 1 <

FIELD SERVICE TEST MODEL: COMPUTER-CONTROLLED U SYSTEM

MANUAL FOR SYSTEM

5. Publication Date August 23, 1973

650.01

7. Al'TiiOK S)

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VtASHi.Vb i UN, D.C. -0-> •

10. project/ I ask. \*ork I'm: N.>. 6505413

1 1. Contract, Grant No. AFTAC T/230/U/NES

Department cf the Air Force

HQ USAF (AFTAC /TAP)

Patrick A.F.E. , Florida 32925

13. 1 ypc of Report & Period Covered

Instruction Manual

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

'6. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) This manual contains an overview 0 f the U system, which uses a small computer to

provide automatic control of up to 15 special-purpose radio receivers. The diagrams

show the overall system configuration, cabling, data flow and computer word bit

assignments

.

17. KEY WORDS (Alphabetical order, sep.ir.uvd i

. ni l Color: ADACS; computer-controlled receivers; U system

13. AVAILABILITY STATEMENT

UNLIMITED.

X l-Q ft OFITCI A ! . Dl TO NTIS.

li )N. DO NO r H I LFaT

19. SIXTRITY ( LAS

i THIS REPORT)

!NCL ASsH'lLD

21. NO. OF PAG1

?0. r; ;; \ \ Y C1.A<S

! 1 til S i' AOEJ

L'NCLASSIITED

U SCOMM-UC