METRIC

MIL-HDBK-1908B

> 16 August 1999
>
> [\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_]{.underline}

SUPERSEDING

> MIL-HDBK-1908A
>
> 25 June 1996

**DEPARTMENT OF DEFENSE**

**HANDBOOK**

**DEFINITIONS OF HUMAN FACTORS TERMS**

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height="1.8145833333333334in"}

**This handbook is for guidance only. Do not cite this document as a
requirement.**

FOREWORD

1\. This Military Handbook is approved for use by all Departments and
Agencies of the Department of Defense.

2\. This handbook is for guidance only. This handbook cannot be cited as
a requirement. If it is, the contractor does not have to comply.

3\. The goals of this handbook are to eliminate definition overlap,
duplication, and conflict and to minimize the length of human factors
(HFAC) standardization documents; therefore, as HFAC documents have been
revised, their definitions were dropped in favor of citing this
handbook.

4\. While this handbook focuses on definitions of human factors terms,
definitions of some non-human factors terms herein have been adopted
from MIL-HDBK-505 since they are used very frequently in HFAC documents
that, typically, have cited MIL-HDBK-505 or used terms that harmonize
with those in MIL-HDBK-505.

5\. Beneficial comments (recommendations, additions, deletions) and any
pertinent data which may be of use in improving this document should be
addressed to Commander, U.S. Army Aviation and Missile Command, ATTN:
AMSAM-RD-SE-TD-ST, Redstone Arsenal, AL 35898-5000 by using the
Standardization Document Improvement Proposal (DD Form 1426) appearing
at the end of this document or by letter.

> CONTENTS

[PARAGRAPH]{.underline} [PAGE]{.underline}

1 SCOPE 1

1.1 Scope 1

1.2 Purpose 1

2 APPLICABLE DOCUMENTS 1

2.1 General 1

2.2 Government documents 1

2.2.1 Specifications, standards, and handbooks 1

2.2.2 Other government documents, drawings, and publications 1

2.3 Non-Government publications 1

2.4 Order of precedence 2

3 DEFINITIONS 3

4 NOTES 36

4.1 Intended use 36

4.2 Subject term (key word) listing 36

4.3 Changes from previous issue 36

[FIGURE]{.underline}

1\. Example of A-duration of actual pressure-time history of an impulse
noise 4

2\. Angle of incidence 6

3\. Scale for conversion between kPa and dB 26

[TABLE]{.underline}

I Metric equivalents, abbreviations, and prefixes 22

[CONCLUDING MATERIAL]{.underline} 37

1\. SCOPE

1.1 [Scope]{.underline}. This handbook defines terms frequently used in
human factors standardization documents by providing common meanings of
such terms to ensure that they will be interpreted consistently and in
the manner intended.

1.2 [Purpose]{.underline}. This handbook is for guidance only. This
handbook cannot be cited as a requirement. If it is, the contractor does
not have to comply.

2\. APPLICABLE DOCUMENTS

2.1 [General]{.underline}. The documents listed below are not
necessarily all of the documents referenced herein, but are the ones
needed in order to fully understand the information provided by this
handbook.

2.2 [Government documents]{.underline}.

2.2.1 [Specifications, standards, and handbooks]{.underline}. The
following standard and handbook form a

part of this document to the extent specified herein. Unless otherwise
specified, the issues of these documents are those listed in the latest
issue of the Department of Defense Index of Specifications and Standards
(DoDISS) and supplement thereto.

STANDARDS

DEPARTMENT OF DEFENSE

MIL-STD-1474 - Noise Limits

HANDBOOKS

DEPARTMENT OF DEFENSE

MIL-HDBK-743 - Anthropometry of U.S. Military Personnel

MIL-HDBK-46855 - Human Engineering Program Tasks and Procedures

(Unless otherwise indicated, copies of the above standards are available
from the Standardization Documents Order Desk, Building 4D, 700 Robbins
Avenue, Philadelphia, PA 19111-5094.)

2.2.2 [Other Government documents, drawings, and
publications]{.underline}.

GUIDES

DEPARTMENT OF DEFENSE

Joint Service Specification Guide 2010 (JSSG 2010) - Crew Systems

Joint Technical Architecture, DoD Human Computer Interface (HCI) Style
Guide

2.3 [Non-Government publications]{.underline}. The following documents
form a part of this handbook to the extent specified herein. Unless
otherwise specified, the issues of the documents which are DoD adopted
are those listed in the latest issue of the DoDISS and supplement
thereto.

AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI)

ANSI S1.1 - Acoustical Terminology

ANSI S1.4 - Sound Level Meters, Specification for (DoD adopted)

ANSI S1.6 - Preferred Frequencies, Frequency Levels, and Band Numbers
for Acoustical Measurements (DoD adopted)

ANSI S3.5 - Calculation of the Articulation Index, Methods for (DoD
adopted)

(Application for copies should be addressed to the American National
Standards Institute, Inc., 11 West 42nd Street, New York, NY 10036.)

AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM)

ASTM SI 10 - Standard Practice for the Use of the International System
of Units (SI): The Modern Metric System (DoD Adopted)

(Application for copies should be addressed to the American Society for
Testing and Materials, 1916 Race Street, Philadelphia, PA 19103-1187.)

INSTITUTE OF ELECTRICAL AND ELECTRONIC ENGINEERS

IEEE SI 10 - Standard Practice for the Use of the International System
of Units (SI): The Modern Metric System (DoD Adopted)

(Application for copies should be addressed to the IEEE Service Center,
P.O. Box 1331, 445 Hoes Lane, Piscataway, NJ 08555-1331)

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION (ISO)

ISO 226 - Acoustics - Normal Equal-Loudness Level Contours.

(Application for copies should be addressed to the American National
Standards Institute, Inc., 11 West 42nd Street, New York, NY 10036.)

COMMISSION INTERNATIONALE DE L\'ECLAIRAGE (CIE)

CIE Pub 15.2 - Colorimetry, 2nd edition

(Application for copies should be addressed to the American National
Standards Institute, Inc., 11 West 42nd Street, New York, NY 10036.)

(Non-Government standards and other publications are normally available
from the organizations that prepare or distribute the documents. These
documents also may be available in or through libraries or other
information services.)

2.4 [Order of precedence]{.underline}. In the event of a conflict
between the text of this document and the references cited herein, the
text of this document takes precedence. Nothing in this document,
however, supersedes applicable laws and regulations unless a specific
exemption has been obtained.

3\. DEFINITIONS

NOTE: Each term appears alphabetically, in bold face, followed by one or
more italicized annotations that associate the definition to its
application(s). The definitions do not necessarily apply to other
applications. Annotations are used as follows:

> *gen* *General human engineering applications*.
>
> *uci* *User/computer interface or interaction*. Applies to terms that
> have specific meaning when used in the context of user-computer
> interaction or supporting human engineering application of computers
>
> *snv* *Sound, noise, vibration*. Applies to materiel design standards
> for acoustics and vibration that involve maximum limits for exposure
> to steady-state or impulse noise,
>
> voice/audio communication, aural non-detectability, or habitability.
>
> *dsi* *Display symbol information*. Applies to design criteria and
> standards for symbolic and alphanumeric information used on
> electronically and optically generated displays\--primarily airborne
> displays. Does not include qualities that affect legibility, such as
> resolution, brightness, uniformity, contrast, flicker, noise, minimum
> line movement, or color, that may appear as *gen* or *uci*
> definitions.
>
> *acq* *Acquisition*. Includes (a) human engineering tasking
> requirements and guidelines, (b) non-human factors acquisition terms
> frequently used to express programmatic human factors provisions, and
> (c) equipment terms used to express human engineering programmatic,
> design, and test provisions.

A term having more than one definition is listed separately for each
application-dependent definition. A term used by several or all
applications is designated as *gen*. Terms for sub-definitions are
underlined and presented in alphabetical order under the major term to
which they apply. Acoustical terms not appearing below are defined in
accordance with ANSI S1.1. Anthropometric terms are defined by
MIL-HDBK-743.

**A-duration (pressure wave duration)** *snv*. The time required for the
pressure to rise to its principal positive peak and return momentarily
to ambient pressure (see Figure 1).

**A-weighted sound level (dBA)** *snv*. Sound pressure level (in
decibels) measured using a sound level meter with an A-weighting
network. The A-weighted response is maximum at 2500 Hz and drops rapidly
as frequency decreases below 1000 Hz and gradually decreases above 4000
Hz, thereby approximating the frequency dependent human response to
moderate sound levels. See ANSI S1.4 for definition of A-weighting
filter characteristics.

**Abort** *uci*. A capability that cancels all user entries in a defined
transaction sequence.

**Accessible** *gen*. An item is considered accessible when it can be
operated, manipulated, serviced, removed, or replaced by the suitably
clothed and equipped user with applicable body dimensions conforming to
the anthropometric range and database specified by the procuring
activity or if not specified by the procuring activity, with applicable
5th to 95th percentile body dimensions. Applicable body dimensions are
those dimensions which are design-critical to the operation,
manipulation, removal, or replacement task.

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***Acq*uisition phases** *acq*:

[Phase 0 - Concept exploration]{.underline}. Phase 0 typically consists
of competitive, parallel short term concept studies. The focus of these
efforts is to define and evaluate the feasibility of alternative
concepts and to provide a basis for assessing the relative merits (i.e.,
advantages and disadvantages, degree of risk) of these concepts a the
next milestone decision point. Analysis of alternatives shall be used a
appropriate to facilitate comparisons of alternative concepts. The most
promising system concepts shall be defined in terms of initial, broad
objectives for cost, schedule, performance, software requirements,
opportunities for tradeoffs, overall *acq*uisition strategy, and test
and evaluation strategy.

[Phase I - Program definition and Risk Reduction]{.underline}. During
this phase, the program shall become defined as one or more concepts,
design approaches, and/or parallel technologies are pursued as
warranted. Assessments of the advantages and disadvantages of
alternative concepts shall be refined Prototyping, demonstrations, and
early operational assessments shall be considered and included as
necessary to reduce risk so that technology, manufacturing and support
risks are will in hand before the next decision point. Cost drivers,
life cycle cost estimates, cost performance trades, interoperability and
acquisition strategy alternatives shall be considered to include
evolutionary and incremental software development.

[Phase II - Engineering and Manufacturing development]{.underline}. The
primary objectives of this phase are to: translate the most promising
design approach into a stable, interoperable, producible, supportable,
and cost effective design; validate the manufacturing or production
process; and, demonstrate system capabilities through testing. Low Rate
Initial Production (LRIP) occurs while the Engineering and Manufacturing
Development phase is still continuing as test results and design fixes
or upgrades are incorporated.

[Phase III - Production, Fielding/Deployment, and Operational
Support]{.underline}. The objectives of this phase are to achieve an
operational capability that satisfies mission needs. Deficiencies
encountered in Developmental Test and Evaluation (DT&E) and Initial
Operational Test and Evaluation (IOT&E) shall be resolved and fixes
verified. The production requirement of this phase does not apply to
ACAT IA acquisition programs or software intensive systems with no
developmental hardware components. During fielding/deployment and
throughout operational support, the potential for modifications to the
fielded/deployed systems continues.

**Action** *uci*. The process of changing the present state of the
system (that is, processing data, carrying out a command).

**Advisory Signal** *gen*. A signal to indicate safe or normal
configuration, condition of performance, operation of essential
equipment, or to attract attention and impart information for routine
action purposes including a signal to indicate a change in system status
that , while important, does not require immediate action on the part of
the operator.

**Aided communication** *snv*. Electrically or electronically enhanced,
real-time, analog or digital voice communications. In aircraft systems,
the communication parts include intra-aircraft, inter-aircraft, and
aircraft-to-ground links.

**Aircraft pre-flight inspection** *gen*. Checking the aircraft prior to
each flight for flight preparedness by performing visual examinations
and operational tests to discover defects and maladjustments which, if
not corrected, could adversely affect safety or mission accomplishment.
Also includes a check to determine that the aircraft has been properly
serviced for the next flight.

**Alpha** *gen*/*uci*. A descriptive term used to define a character set
containing the letters of an ethnic alphabet, and generally punctuation
marks.

**Alphanumeric** *gen*/*uci*. A descriptive term used to define a
character set containing the letters of an ethnic alphabet, the digits Ø
(ZERO) through 9, and generally special symbols and punctuation marks.

![](media/image3.png){width="3.4in" height="2.5in"} **Angle of
incidence** *gen*. The angle between the line of direction of anything
(as a ray of light or line of sight) striking a surface and a line
perpendicular to that surface drawn to the point of contact. See Figure
2.

FIGURE 2. [Angle of Incidence]{.underline}

**Anthropometric dimensions** *gen*. Measured dimensions that describe
the size and shape of the human body. These dimensions are often
presented in the form of summary statistics that

describe the range of body dimensions that are observed in a population.
Anthropometric terms are defined by MIL-HDBK-743.

**Anthropometry** *gen*. The scientific measurement and collection of
data about human physical characteristics and the application
(engineering anthropometry) of these data to the design and evaluation
of systems, equipment, and facilities.

**Articulation index (AI)** *snv*. A predictive estimate of speech
intelligibility. The AI is a weighted number between 0 and 1 that maps
onto speech intelligibility in a non-linear function from 0% to 100%. It
can be used to predict intelligibility using different vocabulary sizes
and complexities. The AI is computed from a weighted sum of
speech-to-noise ratios in several frequency bands. There are three
generally accepted AI methods: 20-band method, the third octave-band
method, and the octave-band method. The 20 -band method is considered
the most accurate and the octave-band method being the least accurate.
See ANSI S3.5. (Also see \"Speech intelligibility.\")

**Assembly** *acq*. A number of parts or subassemblies or any
combination thereof joined together to perform a specific function and
capable of disassembly. (Examples, Power-shovel front fan assembly,
audio frequency amplifier.) Note: The distinction between an assembly
and a subassembly is determined by the individual application. An
assembly in one instance may be a subassembly in another where it forms
a portion of an assembly.

**Attenuating helmets or headsets** *snv*. Hearing protectors that
provide the wearer with electronic communications.

**Aural nondetectability distance** *snv*. The distance at which, for
given conditions, the one-third octave-band pressure levels of a noise
source at a listener\'s location are below both the sound level of a
quiet environment and average hearing in all one-third octave bands. For
a more detailed explanation and examples, see MIL-STD-1474.

**Auxiliary system** *acq*. A system mechanism or structure other than
the airframe, power plant, or armament, e.g., heating and ventilation,
pressurization, defrost and defog, inverters, pumps, auxiliary power
unit (APU).

**Average hearing** *snv*. The binaural free-field hearing threshold of
normal ears for steady-state noise, given in ISO 226.

**B-duration (pressure envelope duration)** *snv*. The duration of the
primary portion of an impulse noise plus the duration of significant
subsequent fluctuations. These durations are considered to be the time
interval during which the envelope of pressure fluctuations \[positive
and negative\] is within 20 dB of the peak pressure level. Significant
subsequent pressure fluctuations are those whose summed duration is
greater than 10% of the duration of the primary portion. The primary
portion of an impulse noise is the period of time followed by a level
that remains 20 dB below the peak pressure level for a significant
duration. For a more detailed explanation and

examples, see MIL-STD-1474.

**Backup** *uci*. A capability that returns a user to the last previous
display, field, or character in a defined transaction sequence. Also
refers to preserving a second copy of files for data protection
purposes.

**Band** *snv*. A continuous range of frequencies. In communications,
the frequency spectrum

between two defined limits.

**Band level** *snv*. The level of the sound or vibration contained
within a particular band.

**Band-center frequency (fc) (geometric)** *snv*. The mid-band frequency
is the geometric mean between the band edge frequencies of a band. The
geometric mean is the square root of the product of the band edge
frequencies (see \"band-edge frequencies, filter\"), fc = (f1 x f2)1/2.

**Band-edge frequencies, filter** *snv*. The upper (f2) and lower (f1)
frequencies, above and below the frequency of maximum response of a
filter, at which the response to a sinusoidal signal is 3 dB below the
maximum response.

**Bandwidth, filter** *snv*. The difference between f1 and f2 (see
\"band-edge frequencies, filter\"). This difference may be expressed in
Hz, as a percentage of the mid-band frequency, or as the interval
between the band-edge frequencies, in terms of octaves or parts thereof,
such as one-third or one-fifteenth.

**Basic item** *acq*. A term used to distinguish an end item of
equipment from individual components, assemblies, subassemblies, and
parts; e.g., overhaul of the basic item weapon system (AH-64 helicopter
air frame including components repaired while on the air frame) versus
overhaul of engines, accessories and components, and assemblies which
have been removed from the basic item and overhauled to meet established
supply requirements for the AH-64 helicopter.

**Battle-short switch** *acq* A switch used on high-priority equipment
designed to bypass or short circuit interlock switches or devices during
emergency conditions.

**Biomedical** *gen*/*acq*. The element including every area that
requires provisions for the promotion of health and safety and in
particular the protection, sustenance, escape, survival and recovery of
personnel employed within the total system environment. This support is
provided for operations, maintenance and support personnel under both
normal and emergency conditions. It also includes health protection from
conditions resulting from system functioning for personnel who are not
included in the total system complex, but who will be affected by the
system.

**Bit (binary digit)** *uci*. 1. A character used to represent one of
the two digits in the numeration system with a base of two, each digit
representing one of two, and only two, possible states of a physical
entity or system. 2. In binary notation, either of the characters 0
or 1. 3. A unit of information equal to one binary decision or the
designation of one of two possible and equally likely states of anything
used to store or convey information.

**C-weighted sound level (dBC)** *snv*. Sound pressure level (in
decibels) measured using a sound level meter with a C-weighting network.
It is generally used to limit the low and high frequency response of the
instrument so that the instrument will not respond to signals outside
the human hearing frequency range at high sound levels. See ANSI S1.4
for definition of C-weighting filters.

**Cancel** *uci*. A capability that regenerates or re-initializes the
current display without processing or retaining any changes made by the
user. Cancel usually means omitting only the action of the last command.

**Case** *acq*. The part of an item of equipment that encloses and
protects the equipment from its surroundings and protects the
surroundings---including personnel---from the equipment.

**Category** *uci*. A grouping of data values along a dimension for
operational purposes. For example, an air traffic controller might be
instructed to implement the same procedures for all aircraft with speeds
in the category of 600 to 800 knots. (Also see \"Value.\")

**Caution signal** *gen*. A signal which alerts the operator to an
impending dangerous condition requiring attention, but not necessarily
immediate action. (See \"Master caution \[warning\] signal\").

**Channel** *uci*. A path along which signals can be sent, e.g., data
channel, output channel.

**Character height** *gen*/*uci*. The vertical distance from the top of
an un-accented alphanumeric to the bottom of the same alphanumeric.

**Chemical warfare a*gen*t** *gen*. A chemical agent in a solid, liquid,
or gas which produces lethal or damaging effects on humans, animals,
plants, or materials, or negatively affects their performance.

**Chromaticity coordinates** *gen*. A three coordinate system for
specifying chromaticity. The chromaticity coordinates can be interpreted
as the fraction of the red primary, the fraction of the green primary
and the fraction of the blue primary needed in a mixture of the
primaries that

matches the given color. (See CIE 1931 and CIE 1976 in CIE Pub 15.2.)

**Clo unit** *gen*. The measurement unit of the insulation value
provided by clothing and defined mathematically as: F/(BTU/hr)(ft2 of
body area). One clo unit is that amount of insulation required to keep a
nude sedentary man comfortable at 70°F, 50% relative humidity in a
normally vented room.

**Coding** *gen*. Use of a system of symbols, shapes, colors or other
variable sensory stimuli to represent specific information.

**Coding characteristics** *dsi*. Readily identifiable attributes
commonly associated with a symbol by means of which such symbols are
differentiated; e.g., size, shape, color.

**Command** *uci*. That part of a computer instruction word that
specifies the operation to be performed.

**Command and control system** *acq* The facilities, equipment,
communications, procedures, and personnel essential to a commander for
planning, directing, and controlling operations of assigned forces
pursuant to the missions assigned.

**Command and control system equipment** *acq*. The main mission
element, equipment and related ground equipment used in collecting,
transmitting, processing, storing and displaying information for command
and control.

**Command entry** *uci*. A single command that causes a computer to
perform a series of steps.

**Command information** *dsi*. Displayed information directing a control
action.

**Command language** *uci*. A type of dialogue in which a user composes
or selects and activiates control entries.

**Common hand tool** *acq*. A tool found in common usage or applicable
to a variety of operations or to a single operation on a variety of
material. Screwdrivers, hammers, and wrenches are examples of common
hand tools.

**Common part** *acq*. A part or component which is generic because (a)
equivalent parts are available from more than one manufacturer and (b)
it is not designed or intended for exclusive use in or by a single
system or piece of equipment.

**Common tool** *acq*. A tool, routinely found in the tool supply of
maintenance organizations for a similar class of system or equipment,
which is generic because it is available from more than one
manufacturer, and is not designed or intended for exclusive use on or
with a single system or piece of equipment.

**Components** *acq*. Those constituent materials, parts, assemblies,
and subassemblies that make up a piece of equipment or a unit. (Also see
"Unit.\")

**Compound number** *uci*. A quantity involving different units of
measure, for example, 3 feet 4 inches or 10 pounds 5 ounces.

**Confirm** *acq*. When used relative to test and evaluation,
\"confirm\" implies a qualitative test that requires comparison of test
results to an applicable requirement(s) (See \"Demonstration\").

**Connector** *acq*. A piece of hardware that joins or attaches lines or
cables to other lines or cables or to items of equipment. The term is
used rather loosely to refer to either of two parts that mate with each
other or to the plug that mates with a receptacle.

**Contrast** *gen*. See \"Luminance contrast.\"

**Control** *gen*. A mechanism used to regulate or guide the operation
of a machine, equipment component, subsystem, or system.

**Control entry** *uci*. User input of data for computer
processing/sequence control (e.g., function key actuation, menu
selection, command entry) whereby the character or symbol and a control
key are jointly activated, requiring computer responses to such inputs.

**Control mode** *uci*. The condition of the keyboard when the control
(CTL) is depressed. In this mode the alpha keys, which are also labeled
with a control character, generate that associated control character.

**Controller** *uci*. Any device used to position the cursor on the
computer monitor screen. (Examples are: mouse, joystick, cursor keys,
light pen, touch screen, track ball.)

**Cover** *acq*. An item of equipment that closes an access opening.

**Critical display** *gen*. A display required for mission success.

**Critical fusion frequency (CFF)** *gen*. The threshold frequency of a
flickering light stimulus at which the light is reported to be
constantly on (i.e., no flicker is discernible).

**Critical task** *acq*. A task requiring human performance which, if
not accomplished in accordance with system requirements, will most
likely have adverse effects on cost, system reliability, efficiency,
effectiveness, or safety. Critical performance is usually part of a
single line or flow in the operation or maintenance cycle of the system.
An example of a single line of flow involving human performance is the
transmission of a message which must be passed for operations or
maintenance cycles to commence or to continue, such as an order to
prepare a missile for launching. If this order is not passed, or if it
is garbled, the entire missile operation cycle may cease to function as
required. A task is also considered critical whenever equipment design
characteristics demand human performance which approaches the limits of
human capabilities (e.g., human performance functions and tasks are too
demanding, information presented to personnel is inadequate to meet
human performance requirements, appropriate information displayed is not
perceived, or controls provided cannot be effectively operated) and
thereby significantly contributes to the occurrence of one or more of
the following conditions, but not necessarily limited thereto:

a\. Jeopardized performance of a mission

b\. Degradation of mission effectiveness or completion from inaccurate
performance; e.g., human entry or response error predicted required
system performance.

c\. Degradation of the circular error probability (CEP) to an
unacceptable level

d\. Delay of a mission beyond acceptable time limits; e.g., human time
to react will not meet required system reaction time

e\. Improper operation resulting in a system "no-go,\" inadvertent
weapons firing, or failure to achieve operational readiness alert

f\. Exceeding predicted times for maintenance personnel and maintenance
ground equipment (MGE) to complete maintenance tasks (As a rule,
performance times will be considered critical if the total maintenance
response time significantly exceeds maintenance analysis estimates, and
affects MGE quantitative requirements.)

g\. Degradation of system equipment below reliability requirements;
i.e., mean time between failures (MTBF) is reduced

h\. The damaging of system equipment, resulting either in a return to a
maintenance facility for major repair, or in unacceptable costs, spare
requirements, or system downtime

i\. A serious compromise of weapons system security

j\. Injury or illness to personnel

k\. Unacceptable degradation of NBC survivability

**Critical warning** *gen*. A warning that indicates a condition which,
if not corrected, will result in mission failure, equipment damage, or
personal injury. (See \"Warning signal.\")

**Cursor** *uci*. A marker on the display screen that indicates the
position where the computer expects the next input or will display the
next output. The cursor may be positioned under computer control or by
the user. (See \"Controller.\")

**Data** *uci*. The raw materials from which a user extracts
information. Data may include numbers, words, pictures, etc.

**Data entry** *uci*. User input of data (numeric, textual, graphic, or
analog) for computer processing and computer responses to such inputs.

**Data field** *uci*. An area of the display screen reserved for user
entry of a data item.

**Data field label** *uci*. An area of the display screen that serves as
a prompt for entering a data item. It usually cannot be changed by a
user.

**Data item** *uci*. A sub-unit of descriptive information or value
classified under a data element. For example, the data element,
"military personnel grade,\" contains data items such as \"sergeant,\"
\"captain,\" and \"colonel.\" Sometimes a data item may contain only a
single character. Data items may be entered by a user or may be supplied
by the computer.

**Data protection** *uci*. Functional capabilities that guard against
unauthorized data access, data tampering, user errors, and computer
failure.

**Data transmission** *uci*. Message exchange among system users, and
also message exchange with other systems. Transmitted data may include
numbers, words, pictures, or other representations of data.

**Data validation** *uci*. Functional capabilities that check data entry
items for correct content or format as defined by software.

**dBA** *snv*. The unit used to express sound level measured through the
A-weighting network of a sound level meter. See \"A-weighted sound level
(dBA).\"

**dBC** *snv*. The unit used to express sound level measured through the
C-weighting network of a sound level meter. See \"C-weighted sound level
(dBC).\"

**dBP** *snv*. The unit used to express peak pressure level as measured
with a peak-reading sound level meter or combination of instruments with
equivalent characteristics, without weighting networks, and with total
rise time not exceeding 1/20 of the measured A-duration.

**Dead-man control** *gen*. A control which requires a continuous
pressure or contact by the operator to maintain machine, equipment
component, subsystem, or system operation. Such operation automatically
returns to a noncritical state once operator pressure or contact is
removed.

**Decibel (dB)** *snv*. A unit to express sound pressure level. The
decibel is the unit of level when the base of the logarithm is the tenth
root of ten, and the quantities concerned are proportional to power. The
dB has meaning only when the referenced quantity is known. The
internationally accepted reference pressure in acoustics is 20
micropascals (µPa) which corresponds to 0 dB. See \"Sound pressure
level.\"

**Decibel (dB) reference level (0 dB)** *snv*. The level that
corresponds to an RMS

pressure of 20 micropascals (µPa).

**Decontamination** *gen*. Use of chemical solution or physical
processes to absorb, destroy, neutralize, or remove nuclear, chemical,
or biological a*gen*ts from persons, objects, or areas.

**Dedicated key** *uci*. A key which produces one code and is never
affected by the position of either the CTL or SHIFT keys.

**De-emphasis** *snv*. The inverse of pre-emphasis, employed to restore
original vowel-consonant amplitude relationships in pre-emphasized
speech; primarily useful in maintaining the \"natural\" sound quality.
(See \"Pre-emphasis.\")

**Default value** *uci*. A predetermined, frequently-used value for a
data field or control entry, intended to reduce required user entry
actions.

**Delimiter** *uci*. A character marking the beginning or end of a unit
of data.

**Demonstrate** *acq*. When used relative to test and evaluation,
\"demonstrate\" implies a qualitative test that does not require
comparison of test results to an applicable requirement(s). (See
\"Confirm.\")

**Depot level maintenance** *acq*. Maintenance performed on material
requiring major overhaul or a complete rebuild of parts, assemblies,
subassemblies, and end items, including the manufacture of parts,
modification, testing, and reclamation as required.

**Determine** *acq*. When used relative to test and evaluation, implies
a quantitative test that does not require comparison of test results to
an applicable requirement(s). (See \"Evaluate.\")

**Developmental test and evaluation (DT&E)** *acq*. Test and evaluation
performed to (1) identify potential operational and technological
limitations of the alternative concepts and design options being
pursued, (2) support the identification of cost-performance trade-offs,
(3) support the identification and description of design risks, (4)
substantiate that contract technical performance and manufacturing
process requirements have been achieved, and (5) support the decision to
certify the system ready for operational test and evaluation.

**Dialogue (or dialog)** *uci*. A structured series of interchanges
between a user and a computer. Dialogues can be computer initiated,
e.g., question and answer, or user initiated, e.g., command languages.

**Dichotic** *snv*. The condition in which the sound stimulus presented
at one ear differs from the sound stimulus presented at the other ear.
The stimulus may differ in sound pressure, frequency, phase, time,
duration, bandwidth, or other characteristics.

**Dimension** *uci*.. A scale or categorization along which data may
vary, taking different values at different times. For example, relevant
dimensions for an aircraft might include its heading, speed, and
altitude.

**Direction designation** *uci*. User entry of directional data
(azimuth, bearing, heading) on a display.

**Display format** *uci*/*gen*. The organization of different types or
elements of data in a display, including information about the data such
as labels, and other user guidance, such as prompts of error messages.
This may also refer to the size of the display or the ratio of the
display width to height.

**Display framing** *uci*. User control of display coverage by display
movement, including paging, scrolling, offset, and expansion.

**Display *gen*eration** *uci*. The means of specification of data
outputs, either by a user or automatically by the computer.

**Display tailoring** *uci*. Designing displays to meet the specific
task needs of a user, rather than providing a *gen*eral display which
can be used for many purposes.

**Display update** *uci*. Regeneration of changed data to show current
status, by user request or automatically by the computer.

**Duty** *acq*. See \"Task analysis.\"

**Effective temperature** *gen*. An empirically determined index which
combines into a single value the effect of temperature, humidity, and
air movement on the sensation of warmth or cold felt by the human body.
The numerical value is that of the temperature of still, saturated air
which would induce an identical sensation.

**Eight-hour time-weighted average sound level (TWA)** *snv*. A
measurement of the employee\'s workday noise environment. The TWA is
that constant noise level, in dBA, slow response, which may cause
hearing loss in 8 hours to the same extent as the exposure to the actual
workday noise. The workday noise environment may or may not last for
8-hours, but the TWA is always computed as if the TWA level was present
for an 8-hour work shift. Implicit in the TWA is a stipulated exchange
rate between sound level and doubling of exposure time.

> TWA = log10

where: T = total workshift time in hours

t = varying time

L(t) = the time varying A-weighted sound pressure level

Q = exchange rate, normally 3 dB.

The TWA value can be calculated from the following alternate expression
when the sound level

takes on a sequence of N constant levels, Li, each lasting for a time
period of Ci hours:

TWA = 85 + log10(D)

where: D=

and: Ti = Limiting exposure time at each A-weighted sound pressure level
=

Li = ith A-weighted sound pressure level.

The exchange rate must be specified when referring to TWA. Note: TWA is
identical to Leq8 with an exchange rate of 3 dB as utilized by U.S. and
international sound and noise standards.

**Electroluminescent device (EL)** *gen*. A device that produces light
through electrical excitation of a phosphor.

**Enter** *uci*. An explicit user action that effects computer
processing of user entries. For example, after typing a series of
numbers, a user might press an ENTER key that will add them to a data
base, subject to data validation.

**Entry** *uci*. See \"Data entry\" or \"Control entry.\"

**Environment** *gen*. The aggregate of all the conditions and
influences including physical location and operating characteristics of
surrounding equipment and occupants, including temperature, humidity,
and contaminants or surrounding air; operational procedures,
acceleration, shock, vibration, and radiation.

**Equipment** *gen*. General term designating any item or group of
items.

**Equipment, powered ground (PGE)** *acq*. An assembly of mechanical
components including an internal combustion engine or motor, gas
turbine, or steam turbine engine mounted as a single unit on an integral
base or chassis. Equipment may pump gases, liquids, or solids; or
produce compressed, cooled, refrigerated or heater air; or generate
electricity and oxygen. Examples of this equipment: portable cleaners,
filters, hydraulic test stands, pumps and welders, air compressors, air
conditioners. Term applies primarily to aeronautical systems.

**Equipment failure** *gen*. Cessation of the ability to meet the
minimum performance requirements of the equipment specifications.
Further, equipment failure shall imply that the minimum specified
performance cannot be restored through permissible readjustment of
operator controls.

**Equipment grades** *snv*. Categories of equipment undergoing
measurements of airborne sound measurements of shipboard equipment to
classify usage-driven acceptance criteria. Equipment grades are defined
below:

[Grade A3]{.underline}. Equipment to be installed in spaces where direct
speech communication must be understood with minimal error and without
repetition over a distance of 2 meters (6-1/2 ft) or less.

[Grade A12]{.underline}. Equipment to be installed in spaces where
direct speech communication must be understood with minimal error and
without repetition over a distance greater than 2 meters (6.5 ft).

[Grade B]{.underline}. Equipment to be placed in spaces where comfort of
personnel in their quarters is the principal consideration.

[Grade C]{.underline}. Equipment to be placed in the sonar room,
sickbay, library, or other spaces requiring low sound levels and which
are not covered in other categories.

[Grade D]{.underline}. Equipment to be placed in spaces where avoidance
of hearing loss is the prime consideration and intelligible speech
communication is not normally required.

[Grade E]{.underline}. Equipment to be placed in high sound level areas
where voice communication is accomplished with high vocal effort and
where amplified speech and telephones are normally available.

**Equivalent A-weighted sound level** *snv*. Equivalent A-weighted sound
level is the level equivalent to the octave-band levels for the
equipment being measured. It is not the weighted sum of the individual
octave-band levels, but an equivalent level based on experience with
spectral shapes of actual shipboard equipment and shipboard spaces.

**Error management** *uci*. Interface design to facilitate the detection
and correction of user errors.

**Evaluate** *acq*. When used relative to test and evaluation,
\"evaluate\" implies a quantitative test that requires comparison of
test results to an applicable requirement(s). (See \"Determine.\")

**Facilities** *acq*. A physical plant, such as real estate and
improvements thereto, including building and equipment, which provides
the means for assisting or making easier the performance of a system
function. The facilities to which this standard apply are those in which
personnel perform system operational or maintenance duties.

**Fail-safe design** *gen*. Design where a failure will not adversely
affect the safe operation of the system, equipment or facility.

**Feedback** *gen*. Product response (e.g., visual, aural, or tactile)
which indicates the extent to which the operator\'s desired effect was
accomplished. Feedback can be either intrinsic or extrinsic. Intrinsic
feedback (feel) is that which the individual senses directly from the
operation of the control devices (e.g., clicks, detents, resistance,
response ratios, stops, control displacement ). Extrinsic feedback is
that which is sensed from an external source that indicates the
consequences of the control action (e.g., aural tones, display changes,
indicator lights).

**Field** *uci*. See \"Data Field.\"

**Field maintenance** *gen*/*acq*. That maintenance authorized and
performed by designated maintenance activities in direct support of
using organizations. It is normally limited to replacement of
unserviceable parts, subassemblies, or assemblies.

**File** *uci*. A collection of data that is stored in a computer,
treated as a single unit by the operating system of the computer.

**Flight member** *snv*. Any crew member or passenger on board an
aircraft. (There is a distinction between flight crew and passengers,
for more information see JSSG - 2010)

**Flight mode** *snv*. In aircraft systems, each operational
activity/maneuver during which noise

levels are effectively constant.

**Focal point** *acq*. An individual designated as a central source of
information or guidance on a specific program or project requiring
coordinated action by two or more agencies. The designation of a focal
point does not relieve any functional area of its basic responsibility.

**Format** *uci*. See \"Display format.\"

**Form filling** *uci*. A type of dialog in which the computer displays
forms containing labeled fields for data entry by a user.

**Framing** *uci*. See \"Display framing.\"

**Full mission capable (FMC)** *acq*. A status code meaning that the
system or equipment has all systems working which are needed to perform
all of its primary missions.

**Function** *uci*. A computer-supported capability provided to users as
an aid for task performance. Examples of functions are position
designation or direction designation.

**Function** *acq*. See \"Task analysis.\"

**Function key** *uci*. A key, such as the SHIFT key, which
init[i]{.underline}ates or modifies a machine function, (e.g., effects a
control entry, instructs the computer to perform a step, or series of
steps) but does not generate or represent a coded character in the
Military Standard Code for Information Exchange (MSCII).

**Government furnished equipment (GFE)** *acq* Equipment furnished by
the Government which is designed into or will otherwise become a part
(or subsystem) of the total system being *acq*uired.

**Hard copy** *uci*/*gen* In computer graphics or telecommunications, a
permanent reproduction of the data displayed or transmitted. The
reproduction may be on any media suitable for direct use by a person.
Note 1: Teletypewriter pages, continuous printed tapes, facsimile pages,
computer

printouts, and radiophoto prints are all examples of hard copy. Note 2:
Magnetic tapes or diskettes or nonprinted punched paper tapes are not
hard copy.

**Head-up display (HUD)** *gen*. A display that produces a virtual image
of symbolic or pictorial information superimposed on the crewmember\'s
forward field-of-view. For aeronautical

systems, the technique results in the combination of flight control and
weapon delivery information with external visual cues from the scene
normally viewed through the windscreen. Specific symbols and formats can
be selectable for a given mode of operation. Take-off, landing,
navigation, hover, bob-up, terrain following/avoidance, sling load
transportation, air-to-air, and weapon delivery modes may be provided.
Video images may also be displayed, such as those from TV, FLIR, or scan
converted radar, along with symbology.

**Hearing conservation criteria** *snv*. Noise exposure limits that,
when exceeded, indicate the need for hearing conservation measures.

**Hearing damage-risk criteria (DRC)** *snv*. Comprehensive statements
about the relation between various descriptive parameters of the noise
exposure (e.g., sound pressure level, exposure time) and the probability
of temporary or permanent hearing loss.

**Hearing Protectors** *snv*. Devices designed primarily to reduce the
noise reaching the auditory system. They may be of any type: earplugs,
noise muffs (circumaural), or attenuating helmets or headsets.

**Helmet-mounted display (HMD)** *gen*. A display that projects video
imagery, symbolic and/or alphanumeric information on a display medium
(e.g., combining glass or visor) into one or both eyes of the
crewmember. In most aeronautical system applications the display medium
is attached to a flight helmet which is a part of a head tracking
system. The line of sight of the helmet is determined by the head
tracking system and a designated sensor is slewed in a one-to-one
angular correspondence with this line of sight. The display medium then
displays the image from the designated sensor: television (TV), forward
looking infrared (FLIR), or scan converted radar. Specific symbols and
formats can be selectable for a given mode of operation.

**Help** *uci*. A capability that displays information upon user request
for on-line guidance. HELP may inform a user generally about system
capabilities, or may provide more specific guidance in data or
information handling transactions.

**Highlighting** *uci*. Emphasizing displayed data or format features in
some way, e.g., through the use of underlining, bolding, or inverse
video.

**Hooking** *uci*. A task performed by a human operator using a display
interactive device (e.g., joystick, mouse) to select/designate specific
display information (e.g., symbols) for further action or modification.

**Horizontal situation display (HSD)** *gen*. An HSD is a display which
aids the crew members in navigation. Basically, it consists of heading,
distance-to-go, bearing-to-destination or some other navigation facility
or reference, track, map, course, aircraft position, and steering error.
Modes may consist of manual, north-up, track-up, data, test, and off.
Selection of map scale factors may also be provided. Navigation update
can be accomplished with the proper computer techniques. The HSD also
has the capability of combining symbols with the map information.
Symbols may be used for annotation of the projected map, such as check
points, various legs of the mission, high-risk areas, ground track
deviation, and radar homing and threat warning. Specific modes and
formats can be selectable for a given mode of operation.

**Hover, in ground effect** *gen*. A condition when the helicopter is
motionless with respect to the ground and the rotor is operating at one
rotor diameter height or less above ground level.

**Human engineering** *gen*. The application of knowledge about human
capabilities and limitations to system or equipment design and
development to achieve efficient, effective, and safe system performance
at minimum cost and manpower, skill, and training demands. Human
engineering assures that the system or equipment design, required human
tasks, and work environment are compatible with the sensory, perceptual,
mental, and physical attributes of the personnel who will operate,
maintain, control and support it.

**Human engineering design criteria** *gen*. Stated limits on design to
achieve the objectives of human engineering. (See \"Human
engineering.\")

**Human factors** *gen*. A body of scientific facts about human
characteristics. The term covers all biomedical and psychosocial
considerations; it includes, but is not limited to, principles and
applications in the areas of human engineering, personnel selection,
training, life support, job performance aids, and human performance
evaluation.

**Human Factors test and evaluation (HFTE)** *acq*. Part of the system
testing effort conducted in accordance with approved test plans. HFTE
includes all testing directed toward validation and evaluation of human
factors analyses, studies, criteria, decisions, and operational and
maintenance design characteristics, and features. These may include
engineering design tests, model tests, mockup evaluations,
demonstrations, and subsystem tests conducted to verify system level
requirements. Human factors tests are a part of system developmental
test and evaluation and operational test and evaluation.

**Human performance** *gen*. A measure of human functions and action in
a specified environment, reflecting the ability of actual users and
maintainers to meet the system\'s performance standards, including
reliability and maintainability, under the conditions in which the
system will be employed.

**Illuminance** *gen*. A measure of the amount of light falling on a
surface. The metric unit for illuminance is lm/m2, or lux (light flux).
(See \"Metric equivalents, abbreviations, and prefixes.\")

**Impulse noise** *snv*. A short burst of acoustic energy consisting of
either a single impulse or a series of impulses. The pressure history of
a single impulse includes a rapid rise to a peak

pressure, followed by a somewhat slower decay of the pressure envelope
to ambient pressure, both occurring within 1 second. A series of
impulses may last longer than 1 second.

**Information** *uci*/*gen* Organized data that users need to perform
their tasks successfully. Information serves as an answer to a user\'s
questions about data and implies effective assimilation of data by a
user. Data that have been processed and formulated by automated or
manual means to satisfy a knowledge requirement for use by a decision
maker.

**Information system** *gen*. A system, whether automated or manual,
that comprises people, machines, and/or methods, organized to collect,
process, transmit, and disseminate data that represent user information.

**Information system** *uci*. A computer-supported, task-oriented tool
designed to help users perform defined information handling tasks.

**Input** *uci*. (1) The data entered into a computer for processing,
(2) the process of entering data or (3) pertaining to the devices that
enter data. (See \"Control entry\" and \"Data entry.\")

**Intermediate level maintenance** *acq* Maintenance that is normally
the responsibility of, and performed by, designated maintenance
activities for direct support of using organizations. Its phases
normally consist of calibrating, repairing, or replacing damaged or
unserviceable parts, components, or assemblies; modification of
material, emergency manufacturing of unavailable parts; and providing
technical assistance to using organizations. Intermediate maintenance is
normally accomplished by the using commands in fixed or mobile shops.

**Interaction** *uci*. See \"Transaction.\"

**Interface** *uci*. A common boundary between automatic data processing
systems or parts of a single system, or between equipment(s) and a user.
(See \"User-system interface.\")

I**nterrupt** *uci*. Stopping an ongoing transaction in order to
redirect the course of the processing. Examples of interrupt options are
ABORT, BACKUP, CANCEL, and RESTART.

**Job** *acq*. See \"Task analysis.\"

**Joystick** *uci*/*gen*. A stick type input device used to provide
continuous control movement. In

computer applications, joysticks are typically used to provide two axis
cursor control on a display screen. Joysticks may be displacement- or
force-operated. A displacement (or isotonic) joystick moves in the
direction it is pushed. Displacement joysticks are usually spring-loaded
so that they return to their center position. A force-operated (or
isometric) joystick has no perceptible movement; its output is a
function of the force applied.

**Justification** *uci*. Alignment of text or numbers with a margin.
Left-justified text is aligned at the left margin; the right margin is
left ragged. Right-justified text is aligned at the right margin; the
left margin is left ragged. Fully-justified text has spacing added
between letters and words so that all lines are the same length,
resulting in the alignment of both margins.

**Keyboard** *uci*. An input device used to enter data by manual
depression of keys which causes the generation of the selected code
element. That area of the device in which keys associated with
characters are arranged

**Keyboard arrangement** *uci*. The positioning of keys with relation to
each other and their association with specific characters.

**Keytop** *uci*. A finger contact member which allows effective
operation of the device, also called a key.

**Label** *uci*. A title or descriptor that helps a user identify
displayed data. (See \"data field label.\")

**Lesson learned** *acq*. A proven experience of value in the conduct of
future programs. It is normally a conclusion drawn from evaluation of
feedback information or from analysis of the performance resulting from
technical and management functional activities. A lesson learned is
usually recorded and eventually incorporated, where applicable, in
regulations, technical manuals, specifications, standards, or handbooks.

**Life support** *acq*. That area of human factors which applies
scientific knowledge to items which require special attention or
provisions for health promotion, biomedical aspects of safety,
protection, sustenance, escape, survival, and recovery of personnel.

**Light-emitting diode (LED)** *gen*. A pn-junction semiconductor device
that emits incoherent optical radiation when biased in the forward
direction. Primarily used in place of incandescent lamps as indicators
and in alphanumeric assemblies.

**Line replaceable unit (LRU)** *acq*. A component, assembly, or
subassembly which is normally removed and replaced as a single unit to
correct a deficiency or malfunction. LRUs may be composed of shop
replaceable units (SRUs) which are generally removed and replaced in a
maintenance shop.

**Liquid crystal display (LCD)** *gen*. A segmented, solid state,
passive display device consisting of a liquid crystal material, composed
of specialized molecules, sandwiched between two conductive plates, at
least one of which is transparent. Transmission of light through the
medium containing the crystals is affected by the orientation of the
crystals. When a current is applied, the orientation of the crystals,
and therefore the transmission characteristics of the medium, are
altered, resulting in contrast between particular segments/pixels and
their background.

**Local tracks** *dsi*. Tracks generated by the co-located sensor(s)
upon which the air defense system relies to acquire targets, e.g.,
tracks obtained from the system\'s own radar. Also known as \"ownership
tracks\".

**Logistic Support Analysis (LSA)** *acq*. The selective application of
scientific and engineering efforts undertaken during the acquisition
process, as part of the system engineering and design processes to
assist in complying with supportability and other Integrated Logistics
Support (ILS) objectives. ILS is a management process to facilitate
development and integration of logistics support elements to *acq*uire,
field and support a system. These elements include: design, maintenance
planning, manpower and personnel, supply support, support equipment,
training, packaging and handling, transport, standardization and
interoperability.

**Lowercase letters** *uci*. The \"small\" letters. Letters that are not
capitalized.

**Luminance** *gen*. The amount of light flux (power) per unit area per
solid angle (steradian) emitted or reflected from a surface. The metric
unit for luminance is candelas per square meter or lumens per steradian
per square meter.

**Luminance contrast** *gen*. The contrast between a figure and its
background equals the difference between the higher luminance (Lmax) and
the lower luminance (Lmin) divided by the lower luminance (Lmin), i.e.,

C = [Lmax - Lmin]{.underline}

Lmin

Related contrast formulae are as follows:

+-----+----+--------------+----------------+--------------+-----------+
|     |    | Luminance    | Luminance      | Modulation   | Contrast  |
|     |    | Contrast     | Contrast (Alt) | Contrast     | Ratio     |
+-----+----+--------------+----------------+--------------+-----------+
| L   | Lm | [Lmax -      | [Lmax -        | [Lmax -      | [Lmax]{.u |
| max | in | Lmin]        | Lmi            | Lmin]        | nderline} |
|     |    | {.underline} | n]{.underline} | {.underline} |           |
|     |    |              |                |              | Lmin      |
|     |    | Lmin         | Lmax           | Lmax + Lmin  |           |
+-----+----+--------------+----------------+--------------+-----------+
| 100 | 50 | 1.0          | 0.50           | 0.33         | 2.0       |
+-----+----+--------------+----------------+--------------+-----------+
| 100 | 25 | 3.0          | 0.75           | 0.60         | 4.0       |
+-----+----+--------------+----------------+--------------+-----------+
| 100 | 10 | 9.0          | 0.90           | 0.82         | 10.0      |
+-----+----+--------------+----------------+--------------+-----------+

For display applications: Lmax is the total luminance of the area with
the higher luminance, including any background or reflected light, as
measured in the specified lighting conditions; Lmin is the luminance of
the area with the lower luminance, as measured under the specified
lighting

conditions, including any reflected light and any stray display
emissions.

**Luminance ratio (LR)** *gen*. The ratio of the target, subject, or
symbol luminance to the surrounding field or background luminance. For
projection systems, the luminance ratio is equal to the light output of
a projector (measured with no film in the projector) reflected off the
screen (image luminance) divided by all the light falling on the screen
(measured from the greatest viewing angle) other than that actually
forming the image (nonimage or background), i.e., LR = L /Ln,

where L = Image or subject luminance and Ln = Nonimage or background
luminance.

**Macro** *uci*. The capability to allow the user to assign a single
name or function key to a defined series of commands for use with
subsequent command entry. Sometimes called \"smart key\" or \"script.\"
Examples of use are storage of addresses or signature blocks that are
frequently used. Usually initiated through use of a function key.

**Maintainability, design for** *gen*. Design considerations directed
toward achieving those combined characteristics of equipment and
facilities which will enable the accomplishment of necessary maintenance
quickly, safely, accurately, and effectively with minimum requirements
for personnel, skills, special tools, and cost.

**Maintenance** *gen*. All actions necessary for retaining material in
(or restoring it to) a serviceable condition. Maintenance includes
servicing, repair, modification, modernization, overhaul, inspection,
condition determination, corrosion control, and initial provisioning of
support items.

**Man-machine interface** *gen*. The actions, reactions, and
interactions between humans and other system components. This also
applies to a multistation, multiperson configuration or system. Term
also defines the properties of the hardware, software or equipment which
constitute conditions for interactions.

**Man-man interface** *gen*. The actions, reactions, and interactions
(i.e., transactions) among persons as they perform jobs, duties, and
tasks to operate and maintain a manned system, including peer-peer and
subordinate-supervisor interactions.

**Management information system (MIS)** *uci*/*acq*. An organized
assembly of resources and procedures required to collect, process, and
distribute data for use in decision making.

**Manpower and personnel requirements** *acq*. The number of trained
personnel required to operate, maintain and support system equipment in
its operational environment. Manpower refers to the number of people and
personnel refers to their skills. Efficient operation of the system, or
piece of equipment, depends in part on the proper mix and skill level of
military and civilian personnel. Information *gen*erated by this element
serves as a basis for manpower and personnel planning and programming
decisions and setting related parameters and constraints on human
engineering analysis and design.

**Masked threshold** *snv*. The sound pressure level, in dB, at which a
signal becomes distinguishable from other signals and/or noise.

**Master caution (warning) signal** *gen*. A signal which indicates that
one or more caution (warning) lights have been actuated. (See \"Caution
signal\" and \"Warning signal.\")

**Materiel design standard** *gen*.. Design standards that provide
requirements to equipment designers and manufacturers.

**Menu** *uci*. A list of options from which a user makes a selection.

**Menu selection** *uci*. A type of dialogue in which the user selects
one item out of a list of displayed alternatives, whether the selection
is by pointing, by entry of an associated option code, or by actuation
of an assigned function key.

**Message** *uci*. Data that are transmitted from one computer user to
another as a discrete transaction or data that are displayed to users to
aid in performing their tasks. (See \"Data transmission\" and \"User
guidance.\")

**Metric equivalents, abbreviations, and prefixes** *gen*. Metric (SI)
units, inch-pound units, and multipliers to convert from metric to
inch-pound units and the converse are presented in

Table I. For more complete listings, see ASTM or IEEE SI 10.

**Mission** *acq*. See \"Task analysis.\"

**Mission area** *acq*. A location in an aircraft occupied by flight
members during a flight mode. A flight member may occupy more than one
mission area during a mission.

TABLE I. [Metric conversions, abbreviations, and prefixes]{.underline}

TO CONVERT FROM TO MULTIPLY BY

ANGLE degree (deg) radian (rad) 0.017 453 29

minute (min) radian (rad) 0.000 290 888

second (sec) radian (rad) 0.000 004 848

radian (rad) degree (deg) 57.295 8

radian (rad) minute (min) 3437.75

radian (rad) second (sec) 206264.0

LENGTH-AREA-VOLUME foot (ft) meter (m) \*0.304 8

foot2 (ft2) meter2 (m2) \*0.092 903 04

foot3 (ft3) meter3 (m3) 0.028 316 85

inch (in) meter (m) \*0.025 4

inch (in) millimeter (mm) \*25.4

inch2 (in2) millimeter (mm2) \*645.16

inch2 (in2) meter2 (m2) \*0.000 645 16

inch3 (in3) meter3 (m3) 0.000 016 387

meter (m) foot (ft) 3.280 84

meter2 (m2) foot2 (ft2) 10.763 9

meter3 (m3) foot3 (ft3) 35.314 7

meter (m) inch (in) 39.370 1

meter2 (m2) inch2 (in2) 1550.00

meter3 (m3) inch3 (in3) 61023.8

millimeter (mm) inch (in) 0.039 37

millimeter2 (mm2) inch2 (in2) 0.001 55

LIGHT footcandle (ft-C) lux (lx) 10.763 91

footlambert (ft-L) candela/meter2 (cd/m2) 3.426 259

lux (lx) footcandle (ft-C) 0.092 903

candela/meter2 (cd/m2) footlambert (ft-L) 0.291 864

WEIGHT, FORCE, ounce (ozf) newton (N) 0.278 013 9

TORQUE, PRESSURE ounce-inch (ozf•in) newton meter (N•m) 0.007 061 55

pound (lb avoirdupois) kilogram (kg) \*0.453 592 37

pound-force (lbf) newton (N) 4.448 222

pound•inch (lbf•in) newton meter (N•m) 0.112 984 8

pound/square inch (psi) pascal (Pa) 6894.757

newton (N) ounce-force (ozf 3.596 94

newton meter (N•m) ounce•inch (ozf•in) 141.611

kilogram (kg) pound (lb) 2.204 62

newton (N) pound-force (lbf) 0.224 809

newton•Meter (N-m) pound•inch (lbf•in) 8.850 75

pascal (Pa) pound/square inch (psi) 133.322

PREFIXES TEMPERATURE CONVERSION

Nano(n) 10-9 Centi(c) 10-2

Micro(µ) 10-6 Kilo(k) 103 oC = 5/9 (oF - 32)

Milli(m) 10-3 Mega(M) 106 oF = 9/5 oC + 32

\*Indicates exact conversion

**Mission profile** *acq*. A time phased description of operational
events and environments an item experieces from beginning to end of a
specific mission identified are tasks, events, durations, operating
conditions and environment.

**Mode** *gen*. Present condition (status) of the product, e.g., off,
standby, on.

**Modified Rhyme Test (MRT)** *snv*. See \"Speech intelligibility.\"

**Mouse** *uci*. A finger- or hand-held computer input device that
generates the coordinates of a position indicator (e.g., converted to
analogous movements of a cursor across a screen) and is operated by
being moved on a flat surface.

**Night vision goggles** *gen*. Goggles which amplify visible and near
infrared energy, allowing a person to see in the dark.

**Night vision goggle compatibility (NVGC)** *gen*/*acq* The phrase NVG
compatible lighting has taken on at least three distinctly different
meanings. The original meaning was the designing of displays or lighting
such that the display of lighting was easily visible or usable by the
unaided eye but did not interfere with the operation of the night vision
goggles. This definition is closest to the \"Friendly\" lighting mode
noted below. The following terms and definitions are subsets of the
phrase \"NVG compatible."

[NVG Secure]{.underline}. visible light emitted from displays is reduced
to the minimum needed to do the mission, and the near IR (infrared)
content is reduced to less than a fraction of

the visible light as specified by the acquiring activity.

[NVG Friendly]{.underline}. Exterior lighting that is fully usable by
people without NVGs (i.e. typically meets FAA requirements for
visibility) but has drastically reduced IR content so that it

can be used while flying formation with aircraft in which NVGs are being
used (for example, going to and from training site through civilian
airspace.)

[NVG Covert - IR lights]{.underline}. Lighting that is filtered so they
are not visible to the naked eye beyond a few tens of feet, intended to
provide illumination so that NVGs will work in areas without adequate
natural light.

**Noise criterion (NC) curves** *snv*. Widely accepted sets of
octave-band pressure levels used as the basis for indoor noise criteria.
These criteria specify the maximum level permitted in each octave band
for various types of communication requirements.

**Noise-cancelling (microphone)** *snv*. A feature that reduces the
masking effect of ambient noise upon speech impressed on a microphone,
usually by providing equal access of the ambient noise to both surfaces
of a diaphragm to achieve approximate equilibrium, effectively causing
the noise to cancel itself out. Since the talker\'s own voice output
impinges on one side of the microphone diaphragm, the talker\'s signals
are not subject to this cancellation, and so are transmitted more
favorably than if both ambient noise and speech fell simultaneously upon
one face of the diaphragm.

**Nuclear, biological, chemical (NBC) survivability** *gen*. The
instantaneous, cumulative, and residual effects of NBC weapons upon a
system including its personnel. NBC survivability describes the
capability of a system to withstand the NBC environment, including
decontamination, without losing the ability to accomplish its mission.
For any system to be considered survivable in an NBC contaminated
battlefield, it must have at least three essential characteristics:
hardness, decontaminability, and compatibility:

[Hardness]{.underline}. The ability of materiel to withstand the
materiel damaging effects of NBC contamination and any decontaminants
and procedures required to remove it.

[Decontaminability]{.underline}. The ability to make personnel and
materiel safe by absorbing, destroying, neutralizing, making harmless,
or removing chemical or biological agents, or by removing radioactive
material clinging to or around them.

[Compatibility]{.underline}. The ability of a system to be effectively
operated, maintained, and resupplied by persons wearing the full NBC
protective ensemble in all climates for which the system is designed,
and for the period specified in the operational requirements document.

**Numeric** *uci*. A descriptive term used to define a character set
containing the digits Ø (ZERO) through 9, and generally a limited number
of punctuation marks.

**Numeric keypad** *uci*. A numeric keypad is a keyboard type entry
device dedicated to the entry of numeric data.

**Octave (or octave band)** *snv*. A band of frequencies in which the
ratio of the upper

band-edge frequency to the lower band-edge frequency is equal to 2:1.
The band-center

frequencies are the preferred frequencies as specified in ANSI S1.6. The
width of an octave

band in Hz is approximately 71 percent of its mid-band frequency.

**One-third octave band** *snv*. One-third octave bands whose
band-center frequencies are preferred one-third octave bands specified
in ANSI S1.6. The width of a one-third octave band is approximately 23
percent of its band-center frequency.

**Operational mode** *gen*.. In ground systems, each activity/maneuver
during which noise levels are effectively constant.

**Operator** *gen*. A human performer; one who operates a (specified)
item; such as a test set operator, a crane operator, a tool operator, a
valve operator (it is used in human factors in the conventional sense as
distinguished from the operations-maintenance dichotomy).

**Operator** *uci*. See \"user.\"

**Optical character recognition (OCR)** *uci*. The machine
identification of printed characters through use of light-sensitive
devices.

**Optical character recognition (OCR) device** *uci*. A device that
transcribes information directly from a hard copy onto a computer memory
device.

**Optimal visual zone** *gen*. Refers to a 30 degree cone symmetrical
about a line from the design eye position extending outward to the
center of the instrument panel, the apex of the cone being at the design
eye.

**Organizational maintenance** *acq*. That maintenance authorized for
the responsibility of and performed by a using organization on its
assigned equipment. In aeronautical systems, organizational maintenance
normally consists of pre-flight, post-flight, and periodic inspection of

aircraft; daily or minor inspection of other material, servicing,
preventive maintenance, calibration

of systems, and removal and replacement of components.

**Output** *uci*. See \"data display.\"

**Overall layout drawings** *acq*. System design drawings which include
but are not limited to: (1) the configuration and arrangement of major
items of equipment for manned stations, such as a pilot\'s or
astronaut\'s station, or launch control officer\'s station, or shipboard
command station; (2) the configuration and arrangement of items of
equipment, such as modular rack or maintenance ground equipment, which
may not be a part of a manned station for operation, but require human
access for maintenance; (3) the arrangement of interior lighting for
operating or maintaining the

equipment; and (4) labels identifying general panel content, e.g.,
flight mission panel, countdown status panel, communications panel, or
malfunction status panel.

**Page** *uci*. The data appearing at one time on a single display
screen. Can also refer to standard keyboard keys used to move from one
\"page\" of data to another or to the process of accomplishing this
action.

**Panel** *gen*. The front face of an assembly, normally used for
mounting controls and displays.

**Panel layout drawings** *acq*. Equipment detail drawings which
include, but are not necessarily limited to: (1) a scale layout of the
controls and displays on each panel or an item of equipment, such as an
astronaut\'s, pilot\'s or launch control officer\'s console; (2) a
description of all symbols used; (3) identification of the color coding
used for displays and controls; (4) the labeling used on each control or
display; and (5) the identification of control type (e.g., alternate
action or momentary) and a clear differentiation between controls and
indicators.

**Panning** *uci*. An orientation of display framing in which a user
conceives of the display frame as moving over a fixed array of data. The
opposite of scrolling.

**Part** *acq*. One piece, or two or more pieces joined together which
are not normally subject to disassembly without destruction of designed
use, (Examples: outer front wheel bearing of a 3/4 ton truck, computer
chip, composition resistor, screw, gear, mica capacitor, audio
transformer, milling cutter.)

**Peak A-weighted sound pressure level** *snv*. The A-weighted sound
pressure level measured by a peak reading sound level meter or a
combination of instruments with equivalent characteristics, such as a
sound level meter and an impact meter, or a sound level meter and a
calibrated oscilloscope, where the sound level meter has a peak sound
pressure level measuring circuit with total rise time of 200
microseconds or less.

**Peak-clipping (of speech signals)** *snv*. A technique for controlling
amplitude relationships in speech by limiting the excursions of
instantaneous peak-amplitudes to improve intelligibility of speech,
usually followed by amplification of the signal to increase the
amplitude of the clipped peaks to their original level, with
proportional increase of the weaker speech sounds.

**Peak pressure level** *snv*. The highest level, in dB, achieved. (Peak
pressure is the highest level, in Pa, achieved). Conversion between
either kPa or psi and dB is shown in Figure 3. The reference pressure is
20 µPa (peak). (See dBP)

**Personal hearing protection** *snv*. Personal protective equipment
(e.g., helmets, headsets, earmuffs, earplugs, or other approved
protective equipment) that attenuates ambient noise levels in the ear
canal.

**Phonetically balanced (PB) monosyllabic word intelligibility test**
*snv*. See \"Speech intelligibility.\"

**Pointer** *dsi*. A transmittable symbol under the direct control of
the operator, used to point to displayed information, for highlighting
or identifying areas of interest.

![](media/image4.png){width="6.49375in" height="7.645833333333333in"}

FIGURE 3. [Scale for conversion between kPa and dB]{.underline}

**Position designation** *uci*. User selection and entry of a position
on a display, or of a displayed item. (See \"Cursor.\")

**Predictive information** *dsi*. Information predicting future status,
condition, or position of a system, or a subsystem.

**Pre-emphasis** *snv*. Systematic distortion of the speech and/or audio
spectrum to attempt to improve intelligibility of speech and/or
signal-to-noise ratio by emphasizing the high frequency (usually 1 kHz
and higher) portion of the speech or other audio signal.

**Primary controls** *gen*. The most important and frequently used
devices designed to control equipment and systems.

**Primary display** *uci*. The display that is most accessible to the
user and usually the one most frequently used.

**Prime visual signal area (PVSA)** *gen*. The PVSA is an area of the
instrument panel

which is enclosed by a circular arc whose radius is 30 cm (12 inches)
and whose center is defined

by the intersection of the top of the instrument panel and the crew
members\' vertical centerline plane. The area is the optimum location on
the instrument panel for the pilot\'s flight instruments and the master
caution and warning lights.

**Prompt** *uci*. A cue or reminder provided by the computer that alerts
and guides the user to take some action.

**Protanope** *gen*. A user with deficient red-sensitive color vision.

**Qualitative information** *dsi*. Information presented by a display in
a manner which permits the display user to assess the information
without requiring attention to an exact numerical quantity.

**Quantitative information** *dsi*. Information presented by a display
in a manner which permits the display user to observe or extract a
numerical value associated with the information. Quantitative
information may be displayed in either digital or analog form.

**Query language** *uci*. A type of dialogue in which users compose
control entries for displaying specified data from a data base.

**Question and answer** *uci*. A type of dialogue in which the computer
displays questions, one at a time, for a user to answer.

**Random incidence corrector** *snv*. A device that reduces the
directionality of free field microphones allowing their use in diffuse
or random incident sound fields.

**Raster-written cathode ray tube display** *gen*. A method of
refreshing the information displayed on a cathode ray tube in which the
electron beam scans the entire screen in some predetermined pattern,
refreshing portions of the screen as necessary. Variations of the raster
method include (1) the noninterlace method, which involve scanning every
line in succession and, when finished with the entire display, returning
to the beginning and repeating the process and (2) the interlace method,
in which every other line is scanned on one pass, the remaining lines
are scanned on the next pass, and the process is repeated.

**Rated engine speed** *snv*. If not specified (for acoustic testing),
10% less than maximum governed engine speed with no load.

**Record** *uci*. A group of related data fields that are operated on as
a single entity in a database.

**Remote tracks** *dsi*. Tracks generated by other than the co-located
sensors upon which the air defense system relies to *acq*uire targets,
e.g., tracks received from interfacing systems.

**Restart** *uci*. A capability that returns a user to the first display
in a defined transaction sequence.

**Risk** *gen*./*acq*. An expression of possible loss of function and/or
degradation in performance in terms of severity and probability.

**Scenario/conditions** *acq*. See \"Task analysis.\"

**Screen** *uci*.. The viewing surface of a cathode ray tube. Also see
\"Page.\"

**Scrolling** *uci*.. An orientation for display framing in which the
user conceives of data as moving behind a fixed display frame. The
opposite of panning or windowing.

**Seat reference point (SRP)** *gen*.. The point at which the center
line of the seat back surface (depressed) and seat bottom surface
(depressed) intersect. When the seat is positioned at the midpoint of
the adjustment range(s), this intersection point is called the neutral
seat reference point (NSRP).

**Sequence control** *uci*.. Logic and means by which user actions and
computer responses are linked to become coherent transactions

**Shift mode** *uci*. (Also shifted mode.) The condition of the keyboard
when a SHIFT key is operated. In this mode, the alphabetic keys are
associated with the uppercase letters, other character keys with the
corresponding upper graphic symbol, and certain function keys with
alternate functional operations.

**Simulator sickness** *gen*. A form of motion sickness induced in a
virtual environment. Symptoms range from cold sweats and stomach
awareness, to vomiting. Depending on their severity, the symptoms may
degrade operator/system performance.

**Soft copy** *uci*. In computer graphics or telecommunications, data
stored, transmitted, or displayed in an electronic format.

**Sound level** *snv*. The quantity in dB measured by a sound level
meter satisfying the requirements of ANSI S1.4. Sound level is the
frequency weighted sound pressure level obtained with the standardized
dynamic characteristics \"fast\" or \"slow\" and weighting A, B, or C.
If the weighting employed is not indicated, A-weighting is understood.

**Sound pressure level (SPL)** *snv*. Ten times the logarithm to the
base 10 of the ratio of the time-mean-square pressure of a sound in a
stated frequency band, to the square of the reference sound pressure in
gases of 20 micropascals, i.e.,

SPL = 10 Log10( )2 = 10 Log10(P2) + 94

where P = the effective (rms) sound pressure in pascals (Pa) or newtons
per square meter (N/m2). (20 µPa = 20 µN/m2 = 0.0002 microbar = 0.0002
dynes/cm2.)

**Source document** *uci*. The user\'s application document, which is a
source of data eventually processed by the computer program. Examples
include time cards, target lists, vouchers, supply codes, parts lists,
and bills of lading.

**Special tools** *acq*. Tools not listed in the Federal Supply Catalog.

**Spectroradiometer** *gen*. A radiometer equipped with a device for
separating (dispersing) the incoming light into its component
wavelengths, used to measure the spectral power distribution.

**Speech intelligibility** *snv*. A measure of the percentage of words,
phrases or sentences correctly understood over a given speech
communication system in a given noise situation. It may be measured by
either the Phonetically Balanced (PB) Monosyllabic Word Intelligibility
Test or the Modified Rhyme Test (MRT). The former consists of a list of
1,000 words in which each word is spoken and written down by a listener.
The latter consists of a list of 300 words in which a word is spoken and
the listener responds on a prepared multiple format selecting one of six
words as the item heard. Speech intelligibility may also be predicted by
the Articulation Index (AI) in which calculation is performed on the
peak-speech-to-root-mean-square noise ratio obtained in selected
frequency bands from 200 to 7,000 Hertz, i.e., peak amplitude of speech
in relation to the root-mean-square amplitude of the background noise.

**Speech signal processing** *snv*. The modification of the electrical
signal representing speech to enhance the capability of a speech
communications channel. Some examples are simple analog processing,
automatic gain control (AGC), frequency shaping, peak clipping, and
syllabic compression.

**Speech spectrum** *snv*. A segment of the range of audible frequencies
containing the sounds of speech, defined as approximately the range from
80 to 8000 Hz.

**Speech-to-noise ratio (peak speech-to-rms noise)** *snv*. The ratio
between the arithmetic mean of peak amplitudes of speech and the root
mean square (rms) amplitude of background noise.

**Standard tools** *acq*. Tools (normally hand tools) used for the
assembly, disassembly,

inspection, servicing, repair and maintenance of equipment, and which
are manufactured by two or more recognized tool manufacturing companies
and listed in those companies\' catalogs.

**State-of-the-art** *acq*. The highest level of scientific and
technical knowledge existing at the time of contract award.

**Status information** *gen*/*dsi*. Current condition information about
the system and its surroundings.

**Steady-state noise** *snv*. A periodic or random variation in
atmospheric pressure at audible frequencies. It may be continuous,
intermittent or fluctuating, with the sound pressure level varying over
a wide range, provided such variations have a duration exceeding 1
second.

**String** *uci*. In the user\'s context, a word, phrase, or number
(string of characters) in the test or file. Normally employed in the
context of causing the computer to search for, find, or replace a
desired \"string.\"

**Stroke-written cathode ray tube display** *gen*. A cathode ray tube in
which the character *gen*erator *gen*erates a succession of short
strokes in sequence that are combined to form a character or symbol.

**Subassembly** *acq*. Two or more units which form a portion of an
assembly or a unit replaceable as a whole, but having a part or parts
which are individually replaceable. (Examples: gun mount stand, window
recoil mechanism, floating piston, telephone dial, IF strip, mounting
board with mounted parts, power shovel dipper stick.)

**Subsystem** *acq*. A combination of sets, groups, etc., which performs
an operational function within a system and is a major subdivision of
the system. (Examples: Data processing subsystem, guidance subsystem,
display subsystem.)

**Subtask** *acq*. See \"Task analysis.\"

**Support equipment (SE)** *acq*. All equipment required to perform the
support function, except that which is an integral part of the mission
equipment. SE includes tools, test equipment, automatic test equipment
(ATE) (when the ATE is accomplishing a support function),
organizational, intermediate, and related computer programs and
software. It does not include any of the equipment required to perform
mission operations functions.

**Symbol** *dsi*. A geometric form or alphanumeric information used to
represent the state of a parameter on a display.

**Symbol size** *dsi*. Actual symbol size at the display, based on
design eye distance from the display, can be calculated using the
following formula:

L = 2D tan (a/2)

where: L = size of symbol at the display

D = design eye distance from the display

a = symbol subtense (degrees) at D

Example: The breakaway symbol is 100 mrad long. What is the size of the
symbol at the display in cm, if the design eye distance is 71 cm (28
inches)?

a = 100 mr X = 5.73 degrees

L = 2(71) tan (5.73/2) = 7.11 cm

The same formula can be used for simple magnifier type HUD displays by
replacing \"D\" with the effective focal length of the HUD optics. This
formula assumes the angle of incidence of viewing the display is 90
degrees. If it is other than 90 degrees, the symbol size should be
increased by

dividing L by the cosine of the angle of deviation from 90 degrees.

**System** *acq*. A composite of equipment, skills, and techniques
capable of performing or supporting an operational role, or both. A
complete system includes all equipment, related facilities, material,
software, services, and personnel required for its operation and support
to the degree that it can be a self-sufficient unit in its intended
operational environment. (Examples: STINGER, AEGIS, F-15.) When GFE is
required for system operation, whether or not operation with GFE occurs
in all cases of system operation, that GFE is part of the system.)

**System layout drawings** *acq*. System design drawings which include
but are not limited to: (a) the configuration and arrangement of items
of equipment for manned stations (such as a pilot\'s station,
astronaut\'s station, launch control officer\'s station, shipboard
command station, and tank commander\'s station) and multiple crew
stations and positions; and (b) the configuration and arrangement of
items of

equipment, such as modular rack or maintenance ground equipment, which
may not be a part of a manned station for operation, but require human
access for maintenance.

**Systems engineering** *acq*. The program manager shall ensure that a
systems engineering process is used to translate operational needs
and/or requirements into a system solution that includes the design,
manufacturing, test and evaluation, and support processes and products.
The systems engineering process shall establish a proper balance between
performance, risk cost, and schedule, employing a top-down iterative
process of requirements analysis, functional analysis and allocation,
design synthesis and verification, and system analysis and control.
Representative human engineering activities in systems engineering may
include the following:

a\. Preparing operationally-realistic mission profiles and mission
scenarios.

b\. Preparing functional flow block diagrams for the system.

c\. Undertaking a functional analysis of each flow block and definition
of operational and support equipment and facilities requirements.

d\. Preparing system and subsystem schematic block diagrams.

e\. Studying detailed functions, environment and technical design
requirements to allocate assignment of tasks to personnel, equipment,
software, or some combination thereof.

f\. Preparing operations and maintenance timeline analyses to determine
system reaction time.

g\. Preparing and analyzing operational and maintenance task data to
determine equipment quantities, personnel loads, and system down-time
for scheduled and unscheduled maintenance.

h\. Considering training implications.

i\. Conducting trade studies.

j\. Participating in preparation of specifications for the system.

k\. Participating in design reviews, demonstrations, and test/evaluation
activities

l\. Influencing design of software and hardware user interfaces and
applicable processes.

**Tailoring** *acq*. The process by which individual requirements
(paragraphs or sentences) of the selected specifications, standards, and
related documents are evaluated to determine the extent to which they
are most available for a specific system and equipment acquisition and
the modification of these requirements to ensure that each achieves an
optimal balance between operational needs and cost. The tailoring
process must, however, conform to provisions of existing regulations
governing human factors engineering program and take care not to exclude
those requirements which are determined as essential for meeting minimum
operational needs.

**Task** *acq*. See \"Task analysis.\"

**Task analysis** *acq*. A systematic method used to develop a
time-oriented description of personnel-equipment/software interactions
brought about by an operator, controller or maintainer in accomplishing
a unit of work with a system or item of equipment. It shows the
sequential and simultaneous manual and intellectual activities of
personnel operating, maintaining or controlling equipment, in addition
to sequential operation of the equipment. It is a part of system
engineering

analysis where system engineering is required. The following taxonomy is
used to inventory or analyze tasks, with mission and scenario conditions
stated by the procuring activity and the remaining levels dependent on
the current phase of system development and purpose (e.g., gross
analysis of tasks, analysis of critical tasks) for which the analysis is
being conducted:

[Mission]{.underline}. What the system is supposed to accomplish, e.g.,
combat reconnaissance.

[Scenario/conditions]{.underline}, Categories of factors or constraints
under which the system will be expected to operate and be maintained,
e.g., day/night, all weather, all terrain operation.

[Function]{.underline}. A broad category of activity performed by a
system, e.g., transportation.

[Job]{.underline}. The combination of all human performance required for
operation and maintenance of one personnel position in a system, e.g.,
driver.

[Duty]{.underline}. A set of operationally-related tasks within a given
job, e.g., driving, weapon servicing, communicating, target detection,
self protection, operator maintenance.

[Task]{.underline}. A composite of related activities (perceptions,
decisions, and responses) performed for an immediate purpose, written in
operator/maintainer language, e.g., change a tire.

[Subtask]{.underline}. An activity (perceptions, decisions and
responses) which fulfills a portion of the immediate purpose within the
task, e.g., remove lug nuts.

[Task element]{.underline}. The smallest logically and reasonably
definable unit of behavior required in completing a task or subtask,
e.g., apply counterclockwise torque to the lug nuts with a lug wrench.\"

**Task element** *acq*. See \"Task analysis.\"

**Task inventory** *gen*. A comprehensive listing of all tasks performed
by system personnel.

**Task statement** *gen*. A task statement is a description of a task.
It is composed of three basic elements: (1) an action verb which states
what is to be accomplished in the task, (2) an object which identifies
what is to be acted upon in the task, and (3) any qualifying phrases
needed to distinguish the task from related or similar activities, limit
and define the scope of the task, and clearly communicate the nature of
the task. The third element is often added only when needed for
clarification.

**Terminal** *uci*. An input/output device used to enter and display
data. Data are usually entered via a keyboard, and are usually displayed
via a video screen (\"soft copy\") or a printer (\"hard copy\").

**Text entry** *uci*. Initial entry and subsequent editing of textual
material, including messages.

**Three-dimensional audio technology (3D audio)** *gen*. A combination
of hardware and software which manipulates a monaural audio signal in
such a way as to give the illusion, when listened to via headphones,
that the sound originates at a particular spatial location.

**Time-weighted average level (Lavg)** *snv*. The time-weighted sound
level dBA that is

derived from the actual varying sound level of the source during a given
sample time (T), Implicit in this derivation is an exchange between
sound level and time of Q dB per doubling of time. The

criterion level is 85 dBA for a duration of 8 hours.

Lavg = log10

where: T = total time in hours

t = varying time

L(t) = the time varying A-weighted sound pressure level

Q = exchange rate, usually 3, 4, 5, or 6 dB.

The Lavg value can be calculated from the following alternate expression
when the sound level takes on a sequence of N constant levels, Li, each
lasting for a time period of Ci hours:

![](media/image5.emf){width="2.2083333333333335in"
height="0.4444444444444444in"}

where: D= $\int_{i = 1}^{N}\frac{C_{i}}{T_{i}}$

Ti = Limiting exposure time at each A-weighted sound pressure level = Li
= ith A-weighted sound pressure level.

The exchange rate must be specified when referring to Lavg.

**Toggle switch** gen/acq. A lever operated control with discrete
positions.

**Total daily exposure (TDE)** *snv*. The ratio of actual daily noise
exposure to allowable daily noise exposure.

**Touch pad** *uci*. A control device that allows the user to control
cursor movement in any direction by moving the finger across the top of
a touch sensitive pad.

**Touch screen** *uci*. A control device that allows the user to
communicate with the computer by touching the screen. Touch screens can
be operated using two different strategies: (1) The first contact
strategy actuates the point at which the operator makes contact with the
display screen; (2) the "last contact" strategy actuates the point at
which the operator withdraws his/her touch from the display screen.

**Trackball** *uci*. A control device with which the user can control
cursor movement in any direction by rotating the ball. Trackballs are
especially useful when it is desirable to move the cursor long distances
quickly.

**Transaction** *uci*. An action by a user followed by a response from
the computer. The term is used here to represent the smallest functional
\"molecule\" of user-computer interaction.

**Transient sounds** *snv*. Sounds that occur during turn-on and
turn-off of the equipment and infrequent sounds that are less than 15
seconds in duration. If sounds occur at intervals of 1/2 second or less,
the sound is considered steady-state sound.

**Transillumination** *gen*. Light passing through a diffusing element
to be viewed, e.g., the illumination produced by edge- or back-lit
sources that make translucent console panels or indicators

visible in the dark. A variety of illuminating sources are available, to
include incandescent, fluorescent, or sandwich-type (electroluminescent
panels).

**Transmission control** *uci*. Controlling the sequence, content,
format, routine, timing, or other data transmission characteristics.

**Trouble shooting** *gen*. Actions performed to isolate and identify
the specific component which caused a malfunction of a system or complex
component.

**Unit** *acq*. An assembly or any combination of parts, subassemblies
and assemblies mounted together normally capable of independent
operation in a variety of situations., (Examples: hydraulic jack,
electric motor, electronic power supply, internal combustion engine,
electric generator, radio receiver.) This term replaces the term
\"component.\" Note: The size of an item is a consideration in some
cases. An electric motor for a clock may be considered as a part
inasmuch as it is not normally subject to disassembly.

**Uppercase letters** *uci*. The \"Capital\" letters.

**User** *uci*. Any person who uses an information system in performing
a job.

**User-computer interface (*UCI*)** *uci*. The modes by which the human
user and the computer communicate information and by which control is
commanded, including areas such as: information presentation, displays,
displayed information, formats and data elements; command modes and
languages; input devices and techniques; dialog, interaction and
transaction modes; timing and pacing of operations; feedback, error
diagnosis, prompting, queuing and job performance aiding; and decision
aiding.

**User-system interface** *uci*. All aspects of information system
design that effect a user\'s participation in information-handling
transactions.

**Value** *uci*. Specified data for a particular dimension, field, or
variable. For example, values for an aircraft\'s speed might be 800
knots during one observation and 500 knots during another. Also see
\"category.\"

**Variable** *uci*. See \"Dimension,\" \"Data field.\"

**Vertical situation display (VSD)** *dsi*. A situation display having
all of the features of an Electronic Attitude Director Indicator (EADI),
with the increased capability of displaying sensor

data. Additional modes may consist of TV, infrared (IR), attack radar,
weapon TV, or terrain-following radar. Specific symbols and formats can
be selectable for a given mode of operation. When any mode, other than
one of the primary EADI modes is selected, the VSD may present basic
symbolic information for flight control superimposed on the sensor data.
VSD formats generally do not use sky/ground shading.

**Vibration level** *snv*. The logarithm of the ratio of a vibratory
quantity to a reference quantity of the same kind, with the base of the
logarithm, the reference quantity, and the kind of level indicated.

**Warning signal** *gen*. A signal which alerts the operator to a
dangerous condition requiring immediate action. (See \"Master caution
\[warning\] signal\").

**Weapon system** *gen*. A composite of equipment, skills, and
techniques that forms an instrument of combat. The complete weapon
system includes all related equipment, material, services, and personnel
required solely for operation, or other major elements of the system, so
that the instrument of combat becomes a self-sufficient unit of striking
power in its intended operational environment.

**Wet bulb globe temperature (WBGT)** *gen*. A meteorological
measurement which can be used as an index to designate conditions of
temperature and humidity at which on-set of heat stress

can be expected at a particular energy expenditure level. It is
calculated as follows:

WBGT = 0.7TWBnp + 0.2Tg + 0.1TA

where TWBnp = non-psychrometric (np) wet-bulb (WB) temperature

Tg = temperature at interior center of a 15.2 cm (6 in) black globe)

TA = non-psychrometric, but shaded, dry bulb (air) temperature.

**Work station** *uci*. The general physical environment in which the
user works. It includes such things as computer terminals, source
documents, desks, chairs, and lighting. Also used to refer to a computer
terminal capable of sophisticated stand-alone operation, such as
computer-aided-design, computer-aided-engineering, and desktop
publishing.

4\. NOTES

(This section contains information of a *gen*eral or explanatory nature
that may be helpful, but is not mandatory.)

4.1 [Intended use]{.underline}. This handbook is intended for use in
conjunction with current human factors and related specifications,
standards, and handbooks to define terms, frequently used in those
documents, and thereby provide consistency, eliminate overlap and
duplication, and minimize repetition. For these same reasons, this
handbook is also intended for reference during the preparation of new
human factors and related specifications, standards, and handbooks.
Telecommunication terms in this handbook are consistent with those in
FED-STD-1037B. Use of telecommunication terms in new human factors
standardization documents that do not appear herein should use or
harmonize with applicable definitions in the current revision of
FED-STD-1037.

4.2. [Subject term (key word) listing]{.underline}.

Abbreviations

Acoustics

Acquisition/programmatic

Acronyms

Display symbology

Human factors engineering

Terminology

User/Computer interface

Vibration

4.3. [Changes from previous issue]{.underline}. The margins of this
handbook are marked with vertical lines to indicate where changes from
or additions to the previous issue were made. The margins are also
marked with asterisks to identify deletions. This was done as a
convenience only and the

Government assumes no liability whatsoever for any inaccuracies in these
notations. Editorial

changes are not indicated by margin notations.

CONCLUDING MATERIAL

Custodians: Preparing activity:

Army - MI Army-MI

Navy - AS (Project HFAC-0089)

Air Force - 11

Review activities:

Army - AR, AT, AV, CR, EA, GL, MD, MR, PT, TE, TM

Navy - CG, EC, MC, ND, OS, PE, SH, TD

Air Force - 01, 10, 13, 19, 31

OSD - HS, SE

DLS - DH

DISA - DC2

NIMA - MP

NSA - NS

Industry associations and professional societies:

AAMI

AIA

ASTM

EIA

HFES

SAE

Civil A*gen*cy Coordinating Activities:

DOT - FAA

NASA - AE

NHTSA - OST