@@
href="/fs-1037/dir-001/_0068.htm" target="main1">0TLP
0TLP: Abbreviation for zero transmission level point.
@@
href="/fs-1037/dir-001/_0069.htm" target="main1">144-line weighting
144-line weighting: In telephony, a noise weighting used in a noise measuring set to measure
line noise as it would be perceived if the line were terminated with a No. 144-receiver, or a
similar instrument. (188) Note: The meter scale readings are in dBrn (144-line).
@@
href="/fs-1037/dir-001/_0070.htm" target="main1">144-receiver weighting
144-receiver weighting: In telephony, a noise weighting used in a noise measuring set to
measure noise across the receiver of an instrument equipped with a No. 144-receiver. (188) Note:
The meter scale readings are in dBrn (144-receiver).
@@
href="/fs-1037/dir-001/_0071.htm" target="main1">(S+N)/N
(S+N)/N: Abbreviation for signal-plus-noise-to-noise ratio.
@@
href="/fs-1037/dir-001/_0072.htm" target="main1">A-condition
A-condition: In a start-stop teletypewriter system, the significant condition of the signal element
that immediately precedes a character signal or block signal and prepares the receiving
equipment for the reception of the code elements. Contrast with start signal.
@@
href="/fs-1037/dir-001/_0073.htm" target="main1">A-D
A-D: Abbreviation for analog-to-digital. See analog transmission.
@@
href="/fs-1037/dir-001/_0074.htm" target="main1">a-law
a-law: See a-law algorithm.
@@
href="/fs-1037/dir-001/_0075.htm" target="main1">a-law algorithm
a-law algorithm: A standard compression algorithm, used in digital communications systems of
the European digital hierarchy, to optimize, i.e., modify, the dynamic range of an analog signal
for digitizing. Note 1: The wide dynamic range of speech does not lend itself well to efficient
linear digital encoding. A-law encoding effectively reduces the dynamic range of the signal,
thereby increasing the coding efficiency and resulting in a signal-to-distortion ratio that is
superior to that obtained by linear encoding for a given number of bits.
@@
href="/fs-1037/dir-001/_0076.htm" target="main1">a
a: Abbreviation for atto (10-18). See metric system .
@@
href="/fs-1037/dir-001/_0077.htm" target="main1">abandoned call
abandoned call: A call in which the call originator disconnects or cancels the call after a
connection has been made, but before the call is established.
@@
href="/fs-1037/dir-001/_0078.htm" target="main1">abbreviated dialing
abbreviated dialing: A telephone service feature that (a) permits the user to dial fewer digits to
access a network than are required under the nominal numbering plan, and (b) is limited to a
subscriber-selected set of frequently dialed numbers. Synonym speed dialing.
@@
href="/fs-1037/dir-001/_0079.htm" target="main1">abort
abort: 1. In a computer or data transmission system, to terminate, usually in a controlled manner,
a processing activity because it is impossible or undesirable for the activity to proceed. 2. In data
transmission, a function invoked by a sending station to cause the recipient to discard or ignore
all bit sequences transmitted by the sender since the preceding flag sequence.
@@
href="/fs-1037/dir-001/_0080.htm" target="main1">abrasive
abrasive: Any of a number of hard materials, such as aluminum oxide, silicon carbide, and
diamond, that are powdered and carefully graded according to particle size, and used to shape
and/or finish optical elements, including the endfaces of optical fibers and connectors. Note: For
finishing the endfaces of optical fiber connectors, abrasive particles are adhered to a substrate of
plastic film, in a fashion after that of sandpaper. The film is in turn supported by a hard, flat
plate. The connector is supported by a fixture that holds it securely in the proper position for
finishing. The grinding motion may be performed manually or by a machine. [After FAA]
@@
href="/fs-1037/dir-001/_0081.htm" target="main1">absolute delay
absolute delay: The time interval or phase difference between transmission and reception of a
signal. (188)
@@
href="/fs-1037/dir-001/_0082.htm" target="main1">absolute gain
absolute gain: 1. Of an antenna, for a given direction and polarization, the ratio of (a) the power
that would be required at the input of an ideal isotropic radiator to (b) the power actually supplied
to the given antenna, to produce the same radiation intensity in the far-field region. Note 1: If no
direction is given, the absolute gain of an antenna corresponds to the direction of maximum
effective radiated power. Note 2: Absolute gain is usually expressed in dB. (188) Synonym
isotropic gain. 2. Of a device, the ratio of (a) the signal level at the output of the device to (b) that
of its input under a specified set of operating conditions. Note 1: Examples of absolute gain are
no-load gain, full-load gain, and small-signal gain. Note 2: Absolute gain is usually expressed in
dB. (188)
@@
href="/fs-1037/dir-001/_0083.htm" target="main1">absolute temperature
absolute temperature: See thermodynamic temperature.
@@
href="/fs-1037/dir-001/_0084.htm" target="main1">absorption
absorption: In the transmission of electrical, electromagnetic, or acoustic signals, the conversion
of the transmitted energy into another form, usually thermal. (188) [After 2196] Note 1:
Absorption is one cause of signal attenuation. Note 2: The conversion takes place as a result of
interaction between the incident energy and the material medium, at the molecular or atomic
level.
@@
href="/fs-1037/dir-001/_0085.htm" target="main1">absorption band
absorption band: A spectral region in which the absorption coefficient reaches a relative
maximum, by virtue of the physical properties of the matter in which the absorption process
takes place. [FAA]
@@
href="/fs-1037/dir-001/_0086.htm" target="main1">absorption coefficient
absorption coefficient: A measure of the attenuation caused by absorption of energy that results
from its passage through a medium. [After 2196] Note 1: Absorption coefficients are usually
expressed in units of reciprocal distance. Note 2: The sum of the absorption coefficient and the
scattering coefficient is the attenuation coefficient.
@@
href="/fs-1037/dir-001/_0087.htm" target="main1">absorption index
absorption index: 1. A measure of the attenuation caused by absorption of energy per unit of
distance that occurs in an electromagnetic wave of given wavelength propagating in a material
medium of given refractive index. Note: The value of the absorption index K ` is given by
the relation where K is the absorption coefficient, is the wavelength in vacuum, and n is the
refractive index of the absorptive material medium. (188) [After 2196] 2. The functional
relationship between the Sun angle--at any latitude and local time--and the ionospheric
absorption. (188)
@@
href="/fs-1037/dir-001/_0088.htm" target="main1">absorption loss
absorption loss: That part of the transmission loss caused by the dissipation or conversion of
electrical, electromagnetic, or acoustic energy into other forms of energy as a result of its
interaction with a material medium.
@@
href="/fs-1037/dir-001/_0089.htm" target="main1">absorption modulation
absorption modulation: Amplitude modulation of the output of a radio transmitter by means of a
variable-impedance circuit that is caused to absorb carrier power in accordance with the
modulating wave.
@@
href="/fs-1037/dir-001/_0090.htm" target="main1">abstract syntax
abstract syntax: In open systems architecture, the specification of application-layer data or
application-protocol control information by using notation rules that are independent of the
encoding technique used to represent the information. (188)
@@
href="/fs-1037/dir-001/_0091.htm" target="main1">abstract syntax notation one (ASN.1)
abstract syntax notation one (ASN.1): A standard, flexible method that (a) describes data
structures for representing, encoding, transmitting, and decoding data, (b) provides a set of
formal rules for describing the structure of objects independent of machine-specific encoding
techniques, (c) is a formal network-management Transmission Control Protocol/Internet Protocol
(TCP/IP) language that uses human-readable notation and a compact, encoded representation of
the same information used in communications protocols, and (d) is a precise, formal notation that
removes ambiguities. (188)
@@
href="/fs-1037/dir-001/_0092.htm" target="main1">ac-dc ringing
ac-dc ringing: Telephone ringing that makes use of both ac and dc voltages and currents. Note:
An alternating current may be used to operate a ringer and direct current to aid the relay action
that stops the ringing when the called telephone is answered.
@@
href="/fs-1037/dir-001/_0093.htm" target="main1">ac
ac: Abbreviation for alternating current.
@@
href="/fs-1037/dir-001/_0094.htm" target="main1">accept
accept: In data transmission, the condition assumed by a primary or secondary station upon
correct receipt of a frame for processing.
@@
href="/fs-1037/dir-001/_0095.htm" target="main1">acceptance
acceptance: The condition that exists when a system or functional unit meets the specified
performance and security requirements.
@@
href="/fs-1037/dir-001/_0096.htm" target="main1">acceptance angle
acceptance angle: In fiber optics, half the vertex angle of that cone within which optical power
may be coupled into bound modes of an optical fiber. Note 1: The axis of the cone is collinear
with the fiber axis, the vertex of the cone is on the fiber end-face, and the base of the cone faces
the optical power source. Note 2: The acceptance angle is measured with respect to the fiber
axis. Note 3: Rays entering an optical fiber at angles greater than the acceptance angle are
coupled into unbound modes. (188) [After 2196]
@@
href="/fs-1037/dir-001/_0097.htm" target="main1">acceptance cone
acceptance cone: In fiber optics, the cone within which optical power may be coupled into the
bound modes of an optical fiber. Note: The acceptance cone is derived by rotating the
acceptance angle about the fiber axis. (188) [After 2196]
@@
href="/fs-1037/dir-001/_0098.htm" target="main1">acceptance pattern
acceptance pattern: 1. Of an antenna, for a given plane, a distribution plot of the off-axis power
relative to the on-axis power as a function of angle or position. (188) [After 2196] Note: The
acceptance pattern is the equivalent of a horizontal or vertical antenna pattern. 2. Of an optical
fiber or fiber bundle, a curve of total transmitted power plotted against the launch angle.
@@
href="/fs-1037/dir-001/_0099.htm" target="main1">acceptance test
acceptance test: A test of a system or functional unit to ensure that contractual requirements are
met. Note: An acceptance test may be performed at the factory or user premises by the user,
vendor, or a third party.
@@
href="/fs-1037/dir-001/_0100.htm" target="main1">acceptance testing
acceptance testing: Operating and testing of a communication system, subsystem, or component,
to ensure that the specified performance characteristics have been met. (188)
@@
href="/fs-1037/dir-001/_0101.htm" target="main1">acceptance trial
acceptance trial: A trial carried out by nominated representatives of the eventual military users of
the weapon or equipment to determine if the specified performance and characteristics have been
met.
@@
href="/fs-1037/dir-001/_0102.htm" target="main1">accepted interference
accepted interference: Interference at a higher level than that defined as permissible interference
and which has been agreed upon between two or more administrations without prejudice to other
administrations. [NTIA] [RR]
@@
href="/fs-1037/dir-001/_0103.htm" target="main1">access-denial time
access-denial time: The time between the start of an access attempt and access failure caused by
access denial, i.e., system blocking. Note: Access denial times are measured only on access
attempts that result in access denial.
@@
href="/fs-1037/dir-001/_0104.htm" target="main1">access
access: 1. The ability and means necessary to store data in, to retrieve data from, to communicate
with, or to make use of any resource of a system. (188) 2. To obtain the use of a resource. 3.
(COMSEC) [The] capability and opportunity to gain detailed knowledge of or to alter
information or material. [NIS] 4. (AIS) [The] ability and means to communicate with (i.e. ,
input to or receive output from), or otherwise make use of any information, resource, or
component in an AIS. Note [for 3 and 4]: An individual does not have "access" if the proper
authority or a physical, technical, or procedural measure prevents him/her from obtaining
knowledge or having an opportunity to alter information, material, resources, or components.
[NIS] 5. An assigned portion of system resources for one data stream of user communications or
signaling. (188)
@@
href="/fs-1037/dir-001/_0105.htm" target="main1">access attempt
access attempt: The process by which one or more users interact with a telecommunications
system to enable initiation of user information transfer. Note: An access attempt begins with an
issuance of an access request by an access originator. An access attempt ends either in successful
access or in access failure.
@@
href="/fs-1037/dir-001/_0106.htm" target="main1">access category
access category: A class to which a user, such as a person, program, process, or equipment, of a
system may be assigned, based on the resources each user is authorized to use.
@@
href="/fs-1037/dir-001/_0107.htm" target="main1">access charge
access charge: A charge made by a local exchange carrier for use of its local exchange facilities
for a purpose such as the origination or termination of traffic that is carried to or from a distant
exchange by an interexchange carrier. Note: Although some access charges are billed directly to
local end users, a very large part of all access charges is paid by interexchange carriers.
@@
href="/fs-1037/dir-001/_0108.htm" target="main1">access code
access code: The preliminary digits that a user must dial to be connected to a particular outgoing
trunk group or line. (188)
@@
href="/fs-1037/dir-001/_0109.htm" target="main1">access contention
access contention: In ISDN applications, synonymous with "contention." See contention (def.
#2).
@@
href="/fs-1037/dir-001/_0110.htm" target="main1">access control
access control: 1. A service feature or technique used to permit or deny use of the components of
a communication system. 2. A technique used to define or restrict the rights of individuals or
application programs to obtain data from, or place data onto, a storage device. 3. The definition
or restriction of the rights of individuals or application programs to obtain data from, or place
data into, a storage device. 4. [The] process of limiting access to the resources of an AIS to
authorized users, programs, processes, or other systems. [NIS] 5. That function performed by the
resource controller that allocates system resources to satisfy user requests. (188)
@@
href="/fs-1037/dir-001/_0111.htm" target="main1">access control message
access control message: A message that is a user request, a resource controller response, or a
request/response between resource controllers. (188)
@@
href="/fs-1037/dir-001/_0112.htm" target="main1">access coupler
access coupler: Deprecated term. See directional coupler.
@@
href="/fs-1037/dir-001/_0113.htm" target="main1">access denial
access denial: 1. Access failure caused by the issuing of a system blocking signal by a
communications system that does not have a call-originator camp-on feature. 2. Access failure
caused by exceeding the maximum access time and nominal system access time fraction during
an access attempt. Synonym system blocking.
@@
href="/fs-1037/dir-001/_0114.htm" target="main1">access failure
access failure: In a communications system, an unsuccessful access that results in termination of
an access attempt in any manner other than initiation of user information transfer between the
intended source and destination (sink) within the specified maximum access time. Note: Access
failure can be the result of access denial, access outage, user blocking, or incorrect access.
@@
href="/fs-1037/dir-001/_0115.htm" target="main1">access group
access group: A group of one or more stations having identical rights to use the available
resources on a PBX, network or host computer.
@@
href="/fs-1037/dir-001/_0116.htm" target="main1">access line
access line: A transmission path between user terminal equipment and a switching center.
@@
href="/fs-1037/dir-001/_0117.htm" target="main1">access node
access node: In switching systems, the point where user traffic enters and exits a
communications network. Note: Access node operations may include various operations, such as
protocol conversion and code conversion.
@@
href="/fs-1037/dir-001/_0118.htm" target="main1">access originator
access originator: The functional entity responsible for initiating a particular access attempt.
Note: An access attempt can be initiated by a source user, a destination user, or the
telecommunications system.
@@
href="/fs-1037/dir-001/_0119.htm" target="main1">access phase
access phase: In an information-transfer transaction, the phase during which an access attempt is
made. Note: The access phase is the first phase of an information-transfer transaction.
@@
href="/fs-1037/dir-001/_0120.htm" target="main1">access point
access point: 1. A point where connections may be made for testing or using particular
communications circuits. (188) 2. In telephony, a junction point in outside plant consisting of a
semipermanent splice at a junction between a branch feeder cable and distribution cables. (188)
@@
href="/fs-1037/dir-001/_0121.htm" target="main1">access request
access request: A control message issued by an access originator for the purpose of initiating an
access attempt.
@@
href="/fs-1037/dir-001/_0122.htm" target="main1">access time
access time: 1. In a telecommunication system, the elapsed time between the start of an access
attempt and successful access. Note: Access time values are measured only on access attempts
that result in successful access. 2. In a computer, the time interval between the instant at which
an instruction control unit initiates a call for data and the instant at which delivery of the data is
completed. (188) 3. The time interval between the instant at which storage of data is requested
and the instant at which storage is started. (188) 4. In magnetic disk devices, the time for the
access arm to reach the desired track and the delay for the rotation of the disk to bring the
required sector under the read-write mechanism.
@@
href="/fs-1037/dir-001/_0123.htm" target="main1">accounting management
accounting management: In network management, a set of functions that (a) enables network
service use to be measured and the costs for such use to be determined and (b) includes all the
resources consumed, the facilities used to collect accounting data, the facilities used to set billing
parameters for the services used by customers, maintenance of the data bases used for billing
purposes, and the preparation of resource usage and billing reports. (188) [After ANSI T1.210]
@@
href="/fs-1037/dir-001/_0124.htm" target="main1">accumulator
accumulator: 1. A register in which one operand can be stored and subsequently replaced by the
result of an arithmetic or logic operation. 2. A storage register. (188) 3. A storage battery. (188)
@@
href="/fs-1037/dir-001/_0125.htm" target="main1">accuracy
accuracy: The degree of conformity of a measured or calculated value to its actual or specified
value. Contrast with precision.
@@
href="/fs-1037/dir-001/_0126.htm" target="main1">ACD
ACD: Abbreviation for automatic call distributor.
@@
href="/fs-1037/dir-001/_0127.htm" target="main1">ACK
ACK: Abbreviation for acknowledge character.
@@
href="/fs-1037/dir-001/_0128.htm" target="main1">acknowledge character (ACK)
acknowledge character (ACK): A transmission control character transmitted by the receiving
station as an affirmative response to the sending station. Note: An acknowledge character may
also be used as an accuracy control character.
@@
href="/fs-1037/dir-001/_0129.htm" target="main1">acknowledgement
acknowledgement: 1. A response sent by a receiver to indicate successful receipt of a
transmission. Note: An example of an acknowledgement is a protocol data unit, or element
thereof, between peer entities, to indicate the status of data units that have been successfully
received. 2 . A message from the addressee informing the originator that the originator's
communication has been received and understood. [After JP1]
@@
href="/fs-1037/dir-001/_0130.htm" target="main1">acknowledgement delay period
acknowledgement delay period: Synonym (loosely) sliding window.
@@
href="/fs-1037/dir-001/_0131.htm" target="main1">acoustic coupler
acoustic coupler: 1. An interface device for coupling electrical signals by acoustical
means--usually into and out of a telephone instrument. (188) 2. A terminal device used to link
data terminals and radio sets with the telephone network. Note: The link is achieved through
acoustic (sound) signals rather than through direct electrical connection.
@@
href="/fs-1037/dir-001/_0132.htm" target="main1">acoustic noise
acoustic noise: An undesired audible disturbance in the audio frequency range. (188)
@@
href="/fs-1037/dir-001/_0133.htm" target="main1">acoustic wave
acoustic wave: A longitudinal wave that (a) consists of a sequence of pressure pulses or elastic
displacements of the material, whether gas, liquid, or solid, in which the wave propagates, (b) in
gases, consists of a sequence of compressions (dense gas) and rarefactions (less dense gas) that
travel through the gas, (c) in liquids, consists of a sequence of combined elastic deformation and
compression waves that travel though the liquid, and (d) in solids, consists of a sequence of
elastic compression and expansion waves that travel though the solid. Note 1: The speed of an
acoustic wave in a material medium is determined by the temperature, pressure, and elastic
properties of the medium. In air, acoustic waves propagate at 332 m/s (1087 ft/s) at 0°C, at
sea level. In air, sound-wave speed increases approximately 0.6 m/s (2 ft/s) for each kelvin above
0°C. Note 2: Acoustic waves audible to the normal human ear are termed sound waves .
[From Weik '89]
@@
href="/fs-1037/dir-001/_0134.htm" target="main1">acousto-optic effect
acousto-optic effect: A variation of the refractive index of a material caused by interaction with
acoustic energy in the form of a wave or pulse. (188) Note: The acousto-optic effect is used in
devices that modulate or deflect light.
@@
href="/fs-1037/dir-001/_0135.htm" target="main1">acousto-optics
acousto-optics: The discipline devoted to the interactions between acoustic waves and light
waves in a material medium. (188) [After 2196] Note: Acoustic waves can be made to modulate,
deflect, and/or focus light waves by causing a variation in the refractive index of the medium.
@@
href="/fs-1037/dir-001/_0136.htm" target="main1">acquisition
acquisition: 1. In satellite communications, the process of locking tracking equipment on a signal
from a communications satellite. (188) 2. The process of achieving synchronization. 3. In servo
systems, the process of entering the boundary conditions that will allow the loop to capture the
signal and achieve lock-on. (188)
@@
href="/fs-1037/dir-001/_0137.htm" target="main1">acquisition and tracking orderwire
acquisition and tracking orderwire: See ATOW.
@@
href="/fs-1037/dir-001/_0138.htm" target="main1">acquisition time
acquisition time: 1. In a communications system, the time interval required to attain
synchronism. 2. In satellite control communications, the time interval required for locking
tracking equipment on a signal from a communications satellite. (188)
@@
href="/fs-1037/dir-001/_0139.htm" target="main1">active device
active device: A device that requires a source of energy for its operation and has an output that is
a function of present and past input signals. Note: Examples of active devices include controlled
power supplies, transistors, LEDs, amplifiers, and transmitters.
@@
href="/fs-1037/dir-001/_0140.htm" target="main1">active laser medium
active laser medium: Within a laser, the material that emits coherent radiation or exhibits gain as
the result of electronic or molecular transitions to a lower energy state or states, from a higher
energy state or states to which it had been previously stimulated. Note: Examples of active laser
media include certain crystals, gases, glasses, liquids, and semiconductors. Synonym laser
medium.
@@
href="/fs-1037/dir-001/_0141.htm" target="main1">active satellite
active satellite: A satellite carrying a station intended to transmit or retransmit radio
communication signals. [NTIA] [RR] (188) Note: An active satellite may perform signal
processing functions such as amplification, regeneration, frequency translation, and link
switching, to make the signals suitable for retransmission.
@@
href="/fs-1037/dir-001/_0142.htm" target="main1">active sensor
active sensor: 1. A detection device that requires input energy from a source other than that
which is being sensed. Note: An example of an active sensor is a photoconductive cell. 2. In
surveillance, a detection device that emits energy capable of being detected by itself. Note: An
example of an active sensor is a measuring instrument that generates a signal, transmits it to a
target, and receives a reflected signal from the target. Information concerning the target is
obtained by comparison of the received signal with the transmitted signal. 3. A measuring
instrument in the Earth exploration-satellite service or in the space research service by means of
which information is obtained by transmission and reception of radio waves. [NTIA] [RR]
@@
href="/fs-1037/dir-001/_0143.htm" target="main1">active star
active star: See star coupler, multiport repeater .
@@
href="/fs-1037/dir-001/_0144.htm" target="main1">activity factor
activity factor: For a communications channel during a specified time interval, such as the busy
hour, the percentage of time that a signal is present in the channel in either direction. (188)
@@
href="/fs-1037/dir-001/_0145.htm" target="main1">ACU
ACU: Abbreviation for automatic calling unit.
@@
href="/fs-1037/dir-001/_0146.htm" target="main1">Ada®
Ada®: The official, high-level computer language of DOD for embedded-computer,
real-time applications as defined in MIL-STD-1815. Note: Ada® is a registered trademark of
the U.S. Government (Ada Joint Program Office).
@@
href="/fs-1037/dir-001/_0147.htm" target="main1">adaptive channel allocation
adaptive channel allocation: In communications system traffic flow control, channel allocation
in which information-handling capacities of channels are not predetermined but are assigned on
demand. Note: Adaptive channel allocation is usually accomplished by means of a multiplexing
scheme.
@@
href="/fs-1037/dir-001/_0148.htm" target="main1">adaptive communications
adaptive communications: Any communications system, or portion thereof, that automatically
uses feedback information obtained from the system itself or from the signals carried by the
system to modify dynamically one or more of the system operational parameters to improve
system performance or to resist degradation. (188) Note: The modification of a system parameter
may be discrete, as in hard-switched diversity reception, or may be continuous, as in a
predetection combining algorithm.
@@
href="/fs-1037/dir-001/_0149.htm" target="main1"> adaptive differential pulse-code modulation
(ADPCM)
adaptive differential pulse-code modulation (ADPCM): Differential pulse-code modulation in
which the prediction algorithm is adjusted in accordance with specific characteristics of the input
signal.
@@
href="/fs-1037/dir-002/_0150.htm" target="main1">adaptive equalization
adaptive equalization: Equalization (a) that is automatically accomplished while traffic is being
transmitted and (b) in which signal characteristics are dynamically adjusted to compensate for
changing transmission path characteristics. (188)
@@
href="/fs-1037/dir-002/_0151.htm" target="main1">adaptive predictive coding (APC)
adaptive predictive coding (APC): Narrowband analog-to-digital conversion that uses a
one-level or multilevel sampling system in which the value of the signal at each sampling instant
is predicted according to a linear function of the past values of the quantized signals. Note: APC
is related to linear predictive coding (LPC) in that both use adaptive predictors. However, APC
uses fewer prediction coefficients, thus requiring a higher sampling rate than LPC.
@@
href="/fs-1037/dir-002/_0152.htm" target="main1">adaptive radio
adaptive radio: A radio that (a) monitors its own performance, (b) monitors the path quality
through sounding or polling, (c) varies operating characteristics, such as frequency, power, or
data rate, and (d) uses closed-loop action to optimize its performance by automatically selecting
frequencies or channels.
@@
href="/fs-1037/dir-002/_0153.htm" target="main1">adaptive routing
adaptive routing: Routing that is automatically adjusted to compensate for network changes such
as traffic patterns, channel availability, or equipment failures. Note: The experience used for
adaptation comes from the traffic being carried.
@@
href="/fs-1037/dir-002/_0154.htm" target="main1">adaptive system
adaptive system: A system that has a means of monitoring its own performance, a means of
varying its own parameters, and uses closed-loop action to improve its performance or to
optimize traffic. (188)
@@
href="/fs-1037/dir-002/_0155.htm" target="main1">ADC
ADC: Abbreviation for analog-to-digital converter, analog-to-digital conversion.
@@
href="/fs-1037/dir-002/_0156.htm" target="main1">ADCCP
ADCCP: Abbreviation for Advanced Data Communication Control Procedures.
@@
href="/fs-1037/dir-002/_0157.htm" target="main1">add-on conference
add-on conference: A service feature that allows an additional party to be added to an
established call without attendant assistance. Note: A common implementation provides a
progressive method that allows a call originator or a call receiver to add at least one additional
party.
@@
href="/fs-1037/dir-002/_0158.htm" target="main1">add mode
add mode: In addition and subtraction operations, a mode in which the decimal marker is placed
at a predetermined location with respect to the last digit entered.
@@
href="/fs-1037/dir-002/_0159.htm" target="main1">added bit
added bit: A bit delivered to the intended destination user in addition to intended user
information bits and delivered overhead bits. Synonym extra bit.
@@
href="/fs-1037/dir-002/_0160.htm" target="main1">added block
added block: Any block, or other delimited bit group, delivered to the intended destination user
in addition to intended user information bits and delivered overhead bits. Synonym extra block.
@@
href="/fs-1037/dir-002/_0161.htm" target="main1">adder-subtracter
adder-subtracter: A device that acts as an adder or subtracter depending upon the control signal
received; the adder-subtracter may be constructed so as to yield a sum and a difference at the
same time. Note: An arithmetic adder-subtracter yields arithmetic sums and differences, whereas
a logical adder-subtracter yields logical sums and differences.
@@
href="/fs-1037/dir-002/_0162.htm" target="main1">adder
adder: 1. A device whose output data are a representation of the sum of the numbers represented
by its input data. Note: An adder may be serial or parallel, digital or analog. 2. A device whose
output data are a representation of the sum of the quantities represented by its input data. Note:
An adder can add things other than representations of numbers. It can add voltages, etc. Analog
adders are not limited to summing representations of numbers. An adder may operate on digital
or analog data.
@@
href="/fs-1037/dir-002/_0163.htm" target="main1">additive white gaussian noise (AWGN)
additive white gaussian noise (AWGN): Synonym white noise.
@@
href="/fs-1037/dir-002/_0164.htm" target="main1">address-indicating group (AIG)
address-indicating group (AIG): A station or address designator, used to represent a set of
specific and frequently recurring combinations of action or information addresses. Note: The
identity of the message originator may also be included in the AIG. An address group is assigned
to each AIG for use as an address designator.
@@
href="/fs-1037/dir-002/_0165.htm" target="main1">address
address: 1. In communications, the coded representation of the source or destination of a
message. (188) 2. In data processing, a character or group of characters that identifies a register,
a particular part of storage, or some other data source or destination. (188) 3. To assign to a
device or item of data a label to identify its location. (188) 4. The part of a selection signal that
indicates the destination of a call. 5. To refer to a device or data item by its address.
@@
href="/fs-1037/dir-002/_0166.htm" target="main1">address field
address field: The portion of a message that contains the source-user address and the
destination-user addresses. Note: In a communications network, the address field is usually
contained within the message header portion of the message. A message usually consists of the
message header, the user data, and a trailer.
@@
href="/fs-1037/dir-002/_0167.htm" target="main1">address message
address message: A message sent in the forward direction that contains (a) address information,
(b) the signaling information required to route and connect a call to the called line, (c)
service-class information, (d) information relating to user and network facilities, and (e)
call-originator identity or call-receiver identity.
@@
href="/fs-1037/dir-002/_0168.htm" target="main1">address message sequencing
address message sequencing: In common-channel signaling, a procedure for ensuring that
address messages are processed in the correct order when the order in which they are received is
incorrect.
@@
href="/fs-1037/dir-002/_0169.htm" target="main1">address part
address part: A part of an instruction that usually contains only an address or part of an address.
@@
href="/fs-1037/dir-002/_0170.htm" target="main1">address pattern
address pattern: A prescribed structure of data used to represent the destination(s) of a block,
message, packet, or other formalized data structure.
@@
href="/fs-1037/dir-002/_0171.htm" target="main1">address resolution protocol (ARP)
address resolution protocol (ARP): A Transmission Control Protocol/Internet Protocol (TCP/IP)
protocol that dynamically binds a Network-Layer IP address to a Data-Link-Layer physical
hardware address, e.g., Ethernet address.
@@
href="/fs-1037/dir-002/_0172.htm" target="main1">address separator
address separator: A character that separates the different addresses in a selection signal.
@@
href="/fs-1037/dir-002/_0173.htm" target="main1">addressability
addressability: 1. In computer graphics, the capability of a display surface or storage device to
accommodate a specified number of uniquely identifiable points. 2. In micrographics, the
capability of a specified field frame to contain a specific number of uniquely identifiable points.
Note: The addressability is usually specified as the number of identifiable horizontal points by
the number of identifiable vertical points, such as 3000 by 4000.
@@
href="/fs-1037/dir-002/_0174.htm" target="main1">addressable point
addressable point: In computer graphics, any point of a device that can be addressed.
@@
href="/fs-1037/dir-002/_0175.htm" target="main1">ADH
ADH: Abbreviation for automatic data handling.
@@
href="/fs-1037/dir-002/_0176.htm" target="main1">adjacent-channel interference
adjacent-channel interference: Extraneous power from a signal in an adjacent channel. (188)
Note 1: Adjacent channel interference may be caused by inadequate filtering, such as incomplete
filtering of unwanted modulation products in frequency modulation (FM) systems, improper
tuning, or poor frequency control, in either the reference channel or the interfering channel, or
both. Note 2: Adjacent-channel interference is distinguished from crosstalk.
@@
href="/fs-1037/dir-002/_0177.htm" target="main1">adjunct service point (ASP)
adjunct service point (ASP): An intelligent-network feature that resides at the intelligent
peripheral equipment and responds to service logic interpreter requests for service processing.
@@
href="/fs-1037/dir-002/_0178.htm" target="main1">administration
administration: 1. Any governmental department or service responsible for discharging the
obligations undertaken in the convention of the International Telecommunication Union and the
Regulations. [RR] 2. Internal management of units. [JP1] 3. The management and execution of
all military matters not included in strategy and tactics. [JP1] 4. In international
telecommunications for a given country, the government agency assigned responsibility for the
implementation of telecommunications standards, regulations, recommendations, practices, and
procedures. 5. In network management, network support functions that ensure that (a) services
are performed, (b) the network is used efficiently, and (c) prescribed service-quality objectives
are met.
@@
href="/fs-1037/dir-002/_0179.htm" target="main1">administrative management complex
(AMC)
administrative management complex (AMC): In network management, a complex that is
controlled by a network provider, and is responsible for and performs network management
functions such as network maintenance. (188) [After ANSI T1.218-1991]
@@
href="/fs-1037/dir-002/_0180.htm" target="main1">ADP
ADP: Abbreviation for automatic data processing.
@@
href="/fs-1037/dir-002/_0181.htm" target="main1">ADP system
ADP system: Synonym computer system.
@@
href="/fs-1037/dir-002/_0182.htm" target="main1">ADPCM
ADPCM: Abbreviation for adaptive differential pulse-code modulation.
@@
href="/fs-1037/dir-002/_0183.htm" target="main1">ADPE
ADPE: Abbreviation for automatic data processing equipment.
@@
href="/fs-1037/dir-002/_0184.htm" target="main1">Advanced Data Communication Control
Procedures (ADCCP)
Advanced Data Communication Control Procedures (ADCCP): A bit-oriented Data-Link-Layer
protocol used to provide point-to-point and point-to-multipoint transmission of data frames that
contain error-control information. Note: ADCCP closely resembles high-level data link control
(HDLC) and synchronous data link control (SDLC).
@@
href="/fs-1037/dir-002/_0185.htm" target="main1">advanced intelligent network (AIN)
advanced intelligent network (AIN): A proposed intelligent-network (IN) architecture that
includes both IN/1+ and IN/2 concepts.
@@
href="/fs-1037/dir-002/_0186.htm" target="main1">advanced television (ATV)
advanced television (ATV): A family of television systems that is intended to be improvements
over current commercial-quality television. Note: The ATV family includes
improved-definition television (IDTV), extended-definition television (EDTV), and
high-definition television (HDTV).
@@
href="/fs-1037/dir-002/_0187.htm" target="main1">AECS
AECS: Abbreviation for Aeronautical Emergency Communications System. See Aeronautical
Emergency Communications System Plan.
@@
href="/fs-1037/dir-002/_0188.htm" target="main1">aerial cable
aerial cable: A communications cable designed for installation on, or suspension from, a pole or
other overhead structure. (188)
@@
href="/fs-1037/dir-002/_0189.htm" target="main1">aerial insert
aerial insert: In a direct-buried or underground cable run, a cable rise to a point above ground,
followed by an overhead run, e.g. , on poles, followed by a drop back into the ground. Note: An
aerial insert is used in places where it is not possible or practical to remain underground, such as
might be encountered in crossing a deep ditch, canal, river, or subway line.
@@
href="/fs-1037/dir-002/_0190.htm" target="main1">aeronautical advisory station
aeronautical advisory station: An aeronautical station used for advisory and civil defense
communications primarily with private aircraft stations. Synonym UNICOM station. [NTIA]
@@
href="/fs-1037/dir-002/_0191.htm" target="main1">aeronautical broadcast station
aeronautical broadcast station: An aeronautical station which makes scheduled broadcasts of
meteorological information and notices to airmen. (In certain instances, an aeronautical broadcast
station may be placed on board a ship.) [NTIA]
@@
href="/fs-1037/dir-002/_0192.htm" target="main1">aeronautical Earth station
aeronautical Earth station: An Earth station in the fixed-satellite service, or, in some cases, in the
aeronautical mobile-satellite service, located at a specified fixed point on land to provide a feeder
link for the aeronautical mobile-satellite service. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0193.htm" target="main1">Aeronautical Emergency Communications
System (AECS) Plan
Aeronautical Emergency Communications System (AECS) Plan: The AECS Plan provides for
the operation of aeronautical communications stations, on a voluntary, organized basis, to
provide the President and the Federal Government, as well as heads of state and local
governments, or their designated representatives, and the aeronautical industry with an
expeditious means of communications during an emergency situation. [47CFR]
@@
href="/fs-1037/dir-002/_0194.htm" target="main1">aeronautical fixed service
aeronautical fixed service: A radiocommunication service between specified fixed points
provided primarily for the safety of air navigation and for the regular, efficient and economical
operation of air transport. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0195.htm" target="main1">aeronautical fixed station
aeronautical fixed station: A station in the aeronautical fixed service. [NTIA][RR]
@@
href="/fs-1037/dir-002/_0196.htm" target="main1">aeronautical mobile-satellite (R) [route]
service
aeronautical mobile-satellite (R) [route] service: An aeronautical mobile-satellite service
reserved for communications relating to safety and regularity of flight, primarily along national
or international civil air routes. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0197.htm" target="main1">aeronautical mobile-satellite (OR) [off-route]
service
aeronautical mobile-satellite (OR) [off-route] service: An aeronautical mobile-satellite service
intended for communications, including those relating to flight coordination, primarily outside
national and international civil air routes. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0198.htm" target="main1">aeronautical mobile-satellite service
aeronautical mobile-satellite service: A mobile-satellite service in which mobile Earth stations
are located on board aircraft; survival craft stations and emergency position-indicating
radiobeacon stations may also participate in this service. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0199.htm" target="main1">aeronautical mobile service
aeronautical mobile service: A mobile service between aeronautical stations and aircraft stations,
or between aircraft stations, in which survival craft stations may participate; emergency
position-indicating radiobeacon stations may also participate in this service on designated
distress and emergency frequencies. [NTIA]
@@
href="/fs-1037/dir-002/_0200.htm" target="main1">aeronautical mobile (R) [route] service
aeronautical mobile (R) [route] service: An aeronautical mobile service reserved for
communications relating to safety and regularity of flight, primarily along national or
international civil air routes. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0201.htm" target="main1">aeronautical mobile (OR) [off-route]
service
aeronautical mobile (OR) [off-route] service: An aeronautical mobile service intended for
communications, including those relating to flight coordination, primarily outside national or
international civil air routes. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0202.htm" target="main1">aeronautical multicom service
aeronautical multicom service: A mobile service not open to public correspondence, used to
provide communications essential to conduct activities being performed by or directed from
private aircraft. [NTIA]
@@
href="/fs-1037/dir-002/_0203.htm" target="main1">aeronautical radionavigation-satellite
service
aeronautical radionavigation-satellite service: A radionavigation-satellite service in which Earth
stations are located on board aircraft. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0204.htm" target="main1">aeronautical radionavigation service
aeronautical radionavigation service: A radionavigation service intended for the benefit and for
the safe operation of aircraft. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0205.htm" target="main1">aeronautical station
aeronautical station: A land station in the aeronautical mobile service. In certain instances, an
aeronautical station may be located, for example, on board ship or on a platform at sea. [NTIA]
[RR]
@@
href="/fs-1037/dir-002/_0206.htm" target="main1">AF
AF: Abbreviation for audio frequency.
@@
href="/fs-1037/dir-002/_0207.htm" target="main1">AFNOR
AFNOR: Acronym for Association Français Normal. France's national standards-setting
organization. Note: AFNOR provides the Secretariat for ISO TC97/SC1, Information
Technology Vocabulary, which includes computers, communications information processing,
and office machines.
@@
href="/fs-1037/dir-002/_0208.htm" target="main1">AGC
AGC: Abbreviation for automatic gain control.
@@
href="/fs-1037/dir-002/_0209.htm" target="main1">AI
AI: Abbreviation for artificial intelligence.
@@
href="/fs-1037/dir-002/_0210.htm" target="main1">AIM
AIM: Abbreviation for amplitude intensity modulation. See intensity modulation.
@@
href="/fs-1037/dir-002/_0211.htm" target="main1">AIN
AIN: Abbreviation for advanced intelligent network.
@@
href="/fs-1037/dir-002/_0212.htm" target="main1">AIOD
AIOD: Abbreviation for automatic identified outward dialing.
@@
href="/fs-1037/dir-002/_0213.htm" target="main1">AIOD leads
AIOD leads: Terminal equipment leads used solely to transmit automatic identified outward
dialing (AIOD) data from a PBX to the public switched telephone network or to switched service
networks (e.g., EPSCS), so that a vendor can provide a detailed monthly bill identifying
long-distance usage by individual PBX stations, tie trunks, or the attendant. . . . [from 47CFR]
@@
href="/fs-1037/dir-002/_0214.htm" target="main1">air-conditioning
air-conditioning: The simultaneous controlling of the characteristics of air, such as temperature,
humidity, cleanliness, motion, and pollutant concentration, in a space to meet the requirements of
the occupants, a process, or equipment. Synonym environmental control.
@@
href="/fs-1037/dir-002/_0215.htm" target="main1">air-ground radiotelephone service
air-ground radiotelephone service: A public radio service between a base station and airborne
mobile stations. [47CFR]
@@
href="/fs-1037/dir-002/_0216.htm" target="main1">air-ground worldwide communications
system
air-ground worldwide communications system: A worldwide military network of ground stations
that (a) provides two-way communications links between aircraft and ground stations for
navigation and control, including air route traffic control and (b) may also provide support for
special functions, such as for civil aircraft providing assistance to military missions and for
meeting communications requirements for aircraft flying distinguished visitors.
@@
href="/fs-1037/dir-002/_0217.htm" target="main1">air portable
air portable: Denotes materiel that is suitable for transport by an aircraft loaded internally or
externally, with no more than minor dismantling and reassembling within the capabilities of user
units. This term must be qualified to show the extent of air portability. [JP1]
@@
href="/fs-1037/dir-002/_0218.htm" target="main1">air sounding
air sounding: Measuring atmospheric phenomena or determining atmospheric conditions,
especially by means of apparatus carried by balloons, rockets, or satellites.
@@
href="/fs-1037/dir-002/_0219.htm" target="main1">air terminal
air terminal: In grounding systems, the lightning rod or conductor placed on or above a building,
structure, or external conductors for the purpose of intercepting lightning. (188)
@@
href="/fs-1037/dir-002/_0220.htm" target="main1">airborne radio relay
airborne radio relay: 1. Airborne equipment used to relay radio transmission from selected
originating transmitters. [JP1] 2. A technique employing aircraft fitted with radio relay stations
for the purpose of increasing the range, flexibility, or physical security of communications
systems.
@@
href="/fs-1037/dir-002/_0221.htm" target="main1">aircraft Earth station
aircraft Earth station: A mobile Earth station in the aeronautical mobile-satellite service located
on board an aircraft. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0222.htm" target="main1">aircraft emergency frequency
aircraft emergency frequency: An international aeronautical emergency frequency, such as 121.5
MHz (civil) and 243.0 MHz (military), for aircraft stations and stations concerned with safety
and regulation of flight along national or international civil air routes and maritime mobile
service stations authorized to communicate for safety purposes.
@@
href="/fs-1037/dir-002/_0223.htm" target="main1">aircraft station
aircraft station: A mobile station in the aeronautical mobile service, other than a survival craft
station, located on board an aircraft. [RR]
@@
href="/fs-1037/dir-002/_0224.htm" target="main1">airdrome control station
airdrome control station: An aeronautical station providing communication between an airdrome
control tower and aircraft. [NTIA] Synonym airport control station .
@@
href="/fs-1037/dir-002/_0225.htm" target="main1">airport control station
airport control station: Synonym airdrome control station .
@@
href="/fs-1037/dir-002/_0226.htm" target="main1">AIS
AIS: Abbreviation for automated information system.
@@
href="/fs-1037/dir-002/_0227.htm" target="main1">alarm center
alarm center: A location that receives local and remote alarms. Note: An alarm center is usually
in a technical control facility. (188)
@@
href="/fs-1037/dir-002/_0228.htm" target="main1">alarm indicator
alarm indicator: A device that responds to a signal from an alarm sensor. Note: Examples of
alarm indicators include bells, lamps, horns, gongs, and buzzers.
@@
href="/fs-1037/dir-002/_0229.htm" target="main1">alarm sensor
alarm sensor: 1. In communications systems, any device that (a) can sense an abnormal
condition within the system and provide a signal indicating the presence or nature of the
abnormality to either a local or remote alarm indicator, and (b) may detect events ranging from a
simple contact opening or closure to a time-phased automatic shutdown and restart cycle. (188)
2. In a physical security system, an approved device used to indicate a change in the physical
environment of a facility or a part thereof. (188) Note: Alarm sensors may also be redundant or
chained, such as when one alarm sensor is used to protect the housing, cabling, or power
protected by another alarm sensor.
@@
href="/fs-1037/dir-002/_0230.htm" target="main1">ALE
ALE: Abbreviation for automatic link establishment.
@@
href="/fs-1037/dir-002/_0231.htm" target="main1">algorithmic language
algorithmic language: An artificial language established for expressing a given class of
algorithms.
@@
href="/fs-1037/dir-002/_0232.htm" target="main1">aligned bundle
aligned bundle: A bundle of optical fibers in which the relative spatial coordinates of each fiber
are the same at the two ends of the bundle. (188) Note: Such a bundle may be used for the
transmission of images. Synonym coherent bundle.
@@
href="/fs-1037/dir-002/_0233.htm" target="main1">all-glass fiber
all-glass fiber: Synonym all-silica fiber .
@@
href="/fs-1037/dir-002/_0234.htm" target="main1">all-silica fiber
all-silica fiber: An optical fiber composed of a silica-based core and cladding. Note: The
presence of a protective polymer overcoat does not disqualify a fiber as an all-silica fiber, nor
does the presence of a tight buffer. [FAA] Synonym all-glass fiber .
@@
href="/fs-1037/dir-002/_0235.htm" target="main1">all trunks busy (ATB)
all trunks busy (ATB): An equipment condition in which all trunks (paths) in a given trunk
group are busy. Note: All-trunks-busy registers do not indicate subsequent attempts to reach
trunk groups.
@@
href="/fs-1037/dir-002/_0236.htm" target="main1">Allan variance
Allan variance: One half of the time average over the sum of the squares of the differences
between successive readings of the frequency deviation sampled over the sampling period. Note:
The Allan variance is conventionally expressed by y2() . The samples are taken with no
dead-time between them. Synonym two-sample variance.
@@
href="/fs-1037/dir-002/_0237.htm" target="main1">allcall
allcall: In adaptive high-frequency (HF) radio automatic link establishment (ALE), a general
broadcast that does not request responses and does not designate any specific addresses. Note:
This essential function is required for emergencies ("HELP"), sounding-type data exchanges, and
propagation and connectivity tracking. [After FED-STD-1045A] (188)
@@
href="/fs-1037/dir-002/_0238.htm" target="main1">allocation (of a frequency band)
allocation (of a frequency band): 1. Entry in the Table of Frequency Allocations of a given
frequency band for the purpose of its use by one or more (terrestrial or space)
radiocommunication services or the radio astronomy service under specified conditions. This
term shall also be applied to the frequency band concerned. [NTIA] [RR] 2. The process of
designating radio-frequency bands for use by specific radio services. (188)
@@
href="/fs-1037/dir-002/_0239.htm" target="main1">allotment (of a radio frequency or radio
frequency channel)
allotment (of a radio frequency or radio frequency channel): Entry of a designated frequency
channel in an agreed plan, adopted by a component Conference, for use by one or more
administrations for a (terrestrial or space) radiocommunication service in one or more identified
countries or geographical areas and under specified conditions. [NTIA]
@@
href="/fs-1037/dir-002/_0240.htm" target="main1">alpha profile
alpha profile: See power-law index profile .
@@
href="/fs-1037/dir-002/_0241.htm" target="main1">alphabet
alphabet: 1. An ordered set of all the letters used in a language, including letters with diacritical
signs where appropriate, but not including punctuation marks. 2. An ordered set of all the
symbols used in a language, including punctuation marks, numeric digits, nonprinting control
characters, and other symbols. Note: Examples of alphabets include the Roman alphabet, the
Greek alphabet, the Morse Code, and the 128 characters of the American Standard Code for
Information Interchange (ASCII) [IA No. 5]. (188)
@@
href="/fs-1037/dir-002/_0242.htm" target="main1">alphabet translation
alphabet translation: Deprecated synonym for alphabet transliteration. See alphabet
transliteration.
@@
href="/fs-1037/dir-002/_0243.htm" target="main1">alphabet transliteration
alphabet transliteration: The substitution of the characters of one alphabet for the corresponding
characters of a different alphabet, usually accomplished on a character-by-character basis. (188)
Note 1: An example of alphabet transliteration is the substitution of the Roman letters a, b, and p
for the Greek letters , , and , respectively. Note 2: Alphabet transliteration is reversible. Note 3:
Alphabet transliteration often becomes necessary in telecommunications systems because of the
different alphabets and codes used worldwide. Note 4: In alphabet transliteration, no
consideration is given to the meaning of the characters or their combinations.
@@
href="/fs-1037/dir-002/_0244.htm" target="main1">alphabetic character set
alphabetic character set: A character set that contains letters and may contain control characters,
special characters, and the space character, but not digits.
@@
href="/fs-1037/dir-002/_0245.htm" target="main1">alphabetic code
alphabetic code: A code according to which data are represented through the use of an alphabetic
character set.
@@
href="/fs-1037/dir-002/_0246.htm" target="main1">alphabetic string
alphabetic string: 1. A string consisting solely of letters from the same alphabet. 2. A character
string consisting solely of letters and associated special characters from the same alphabet.
@@
href="/fs-1037/dir-002/_0247.htm" target="main1">alphabetic word
alphabetic word: 1. A word consisting solely of letters from the same alphabet. 2. A word that
consists of letters and associated special characters, but not digits.
@@
href="/fs-1037/dir-002/_0248.htm" target="main1">alphanumeric
alphanumeric: 1. Pertaining to a character set that contains letters, digits, and sometimes other
characters, such as punctuation marks. (188) 2. Pertaining to a set of unique bit patterns that are
used to represent letters of an alphabet, decimal digits, punctuation marks, and other special signs
and symbols used in grammar, business, and science, such as those displayed on conventional
typewriter keyboards.
@@
href="/fs-1037/dir-002/_0249.htm" target="main1">alphanumeric character set
alphanumeric character set: A character set that contains both letters and digits, special
characters, and the space character.
@@
href="/fs-1037/dir-002/_0250.htm" target="main1">alphanumeric code
alphanumeric code: 1. A code derived from an alphanumeric character set. 2. A code that, when
used, results in a code set that consists of alphanumeric characters.
@@
href="/fs-1037/dir-002/_0251.htm" target="main1">alphanumeric data
alphanumeric data: Data represented by letters, digits, and sometimes by special characters and
the space character.
@@
href="/fs-1037/dir-002/_0252.htm" target="main1">altazimuth mount
altazimuth mount: A mounting, e.g. , for a directional antenna, in which slewing takes place in
(a) the plane tangent to the surface of the Earth or other frame of reference and (b) elevation
about, i.e., above or below, that plane. Synonym x-y mount.
@@
href="/fs-1037/dir-002/_0253.htm" target="main1">alternate mark inversion (AMI) signal
alternate mark inversion (AMI) signal: A pseudoternary signal, representing binary digits, in
which (a) successive "marks" are of alternately positive and negative polarity and the absolute
values of their amplitudes are normally equal and (b) "spaces" are of zero amplitude.
@@
href="/fs-1037/dir-002/_0254.htm" target="main1">alternate party
alternate party: In multilevel precedence and preemption, the call receiver, i.e. , the destination
user, to which a precedence call will be diverted. Note 1: Diversion will occur when the
response timer expires, when the call receiver is busy on a call of equal or higher precedence, or
when the call receiver is busy with access resources that are non-preemptable. Note 2: Alternate
party diversion is an optional terminating feature that is subscribed to by the call receiver. Thus,
the alternate party is specified by the call receiver at the time of subscription. (188)
@@
href="/fs-1037/dir-002/_0255.htm" target="main1">alternate routing
alternate routing: The routing of a call or message over a substitute route when a primary route is
unavailable for immediate use. (188)
@@
href="/fs-1037/dir-002/_0256.htm" target="main1">altitude of the apogee or of the perigee
altitude of the apogee or of the perigee: The altitude of the apogee or perigee above a specified
reference surface serving to represent the surface of the Earth. [NTIA] [RR] Note: In technical
usage, the definite article is not used with the term apogee or perigee alone. A body orbiting the
Earth is said simply to be "at apogee" or "at perigee." It may, however, properly be said to be "at
the point of apogee" or "at the point of perigee."
@@
href="/fs-1037/dir-002/_0257.htm" target="main1">ALU
ALU: Abbreviation for arithmetic and logic unit.
@@
href="/fs-1037/dir-002/_0258.htm" target="main1">AM
AM: Abbreviation for amplitude modulation.
@@
href="/fs-1037/dir-002/_0259.htm" target="main1">AMA
AMA: Abbreviation for automatic message accounting.
@@
href="/fs-1037/dir-002/_0260.htm" target="main1">amateur-satellite service
amateur-satellite service: A radiocommunication service using space stations on Earth satellites
for the same purposes as those of the amateur service. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0261.htm" target="main1">amateur service
amateur service: A radiocommunication service for the purpose of self-training,
intercommunication and technical investigation carried out by amateurs, that is, by duly
authorized persons interested in radio technique solely with a personal aim and without pecuniary
interest. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0262.htm" target="main1">amateur station
amateur station: A station in the amateur service. [NTIA] [RR]
@@
href="/fs-1037/dir-002/_0263.htm" target="main1">ambient noise level
ambient noise level: The level of acoustic noise existing at a given location, such as in a room,
in a compartment, or at a place out of doors. Note 1: Ambient noise level is measured with a
sound level meter. Note 2: Ambient noise level is usually measured in dB above a reference
pressure level of 0.00002 Pa, i.e., 20 Pa (micropascals) in SI units. A pascal is a newton per
square meter. Note 3: In the centimeter-gram-second system of units, the reference level for
measuring ambient noise level is 0.0002 dyn/cm2. (188) Synonym room noise level.
@@
href="/fs-1037/dir-002/_0264.htm" target="main1">ambient temperature
ambient temperature: The temperature of air or other media in a designated area, particularly the
area surrounding equipment. (188)
@@
href="/fs-1037/dir-002/_0265.htm" target="main1">AME
AME: Abbreviation for amplitude modulation equivalent, automatic message exchange. See
compatible sideband transmission.
@@
href="/fs-1037/dir-002/_0266.htm" target="main1">American National Standards Institute
(ANSI)
American National Standards Institute (ANSI): The U.S. standards organization that establishes
procedures for the development and coordination of voluntary American National Standards.
@@
href="/fs-1037/dir-002/_0267.htm" target="main1">American Standard Code for Information
Interchange (ASCII)
American Standard Code for Information Interchange (ASCII): See ASCII.
@@
href="/fs-1037/dir-002/_0268.htm" target="main1">AMI
AMI: Abbreviation for alternate mark inversion. See alternate mark inversion signal.
@@
href="/fs-1037/dir-002/_0269.htm" target="main1">AMI violation
AMI violation: A "mark" that has the same polarity as the previous "mark" in the transmission
of alternate mark inversion (AMI) signals. Note: In some transmission protocols, AMI violations
are deliberately introduced to facilitate synchronization or to signal a special event.
@@
href="/fs-1037/dir-002/_0270.htm" target="main1">amplifier
amplifier: See fiber amplifier, optical repeater .
@@
href="/fs-1037/dir-002/_0271.htm" target="main1">amplitude-vs.-frequency distortion
amplitude-vs.-frequency distortion: Distortion in a transmission system caused by nonuniform
attenuation, or gain, in the system with respect to frequency under specified operating conditions.
(188) Synonym frequency distortion.
@@
href="/fs-1037/dir-002/_0272.htm" target="main1">amplitude distortion
amplitude distortion: Distortion occurring in a system, subsystem, or device when the output
amplitude is not a linear function of the input amplitude under specified conditions. (188) Note:
Amplitude distortion is measured with the system operating under steady-state conditions with a
sinusoidal input signal. When other frequencies are present, the term "amplitude" refers to that
of the fundamental only.
@@
href="/fs-1037/dir-002/_0273.htm" target="main1">amplitude equalizer
amplitude equalizer: A corrective network that is designed to modify the amplitude
characteristics of a circuit or system over a desired frequency range. (188) Note: Such devices
may be fixed, manually adjustable, or automatic.
@@
href="/fs-1037/dir-002/_0274.htm" target="main1">amplitude hit
amplitude hit: See hit (def. #1).
@@
href="/fs-1037/dir-002/_0275.htm" target="main1">amplitude intensity modulation (AIM)
amplitude intensity modulation (AIM): Deprecated term. See intensity modulation.
@@
href="/fs-1037/dir-002/_0276.htm" target="main1">amplitude keying
amplitude keying: Keying in which the amplitude of a signal is varied among the members of a
set of discrete values. (188)
@@
href="/fs-1037/dir-002/_0277.htm" target="main1">amplitude modulation (AM)
amplitude modulation (AM): Modulation in which the amplitude of a carrier wave is varied in
accordance with some characteristic of the modulating signal. (188) Note: Amplitude
modulation implies the modulation of a coherent carrier wave by mixing it in a nonlinear device
with the modulating signal to produce discrete upper and lower sidebands, which are the sum and
difference frequencies of the carrier and signal. The envelope of the resultant modulated wave is
an analog of the modulating signal. The instantaneous value of the resultant modulated wave is
the vector sum of the corresponding instantaneous values of the carrier wave, upper sideband,
and lower sideband. Recovery of the modulating signal may be by direct detection or by
heterodyning.
@@
href="/fs-1037/dir-002/_0278.htm" target="main1">amplitude modulation equivalent (AME)
amplitude modulation equivalent (AME): Synonym compatible sideband transmission.
@@
href="/fs-1037/dir-002/_0279.htm" target="main1">AMPS
AMPS: Abbreviation for automatic message processing system.
@@
href="/fs-1037/dir-002/_0280.htm" target="main1">AMTS
AMTS: Abbreviation for automated maritime telecommunications system.
@@
href="/fs-1037/dir-002/_0281.htm" target="main1">analog-to-digital (A-D) coder
analog-to-digital (A-D) coder: Synonym analog-to-digital converter (ADC).
@@
href="/fs-1037/dir-002/_0282.htm" target="main1">analog-to-digital converter (ADC)
analog-to-digital converter (ADC): A device that converts an analog signal to a digital signal
that represents equivalent information. (188) Synonyms analog-to-digital (A-D) coder,
analog-to-digital (A-D) encoder.
@@
href="/fs-1037/dir-002/_0283.htm" target="main1">analog-to-digital (A-D) encoder
analog-to-digital (A-D) encoder: Synonym analog-to-digital converter (ADC).
@@
href="/fs-1037/dir-002/_0284.htm" target="main1">analog computer
analog computer: A device that performs operations on data that are represented within the
device by continuous variables having a physical resemblance to the quantities being represented.
Note: The earliest analog computers were constructed with purely mechanical components, such
as levers, cogs, cams, discs, and gears. These components represented the quantities being
manipulated or the operator-inserted values. Modern analog computers usually employ electrical
parameters, such as voltages, resistances, or currents to represent the quantities being
manipulated.
@@
href="/fs-1037/dir-002/_0285.htm" target="main1">analog data
analog data: Data represented by a physical quantity that is considered to be continuously
variable and has a magnitude directly proportional to the data or to a suitable function of the data.
(188)
@@
href="/fs-1037/dir-002/_0286.htm" target="main1">analog decoding
analog decoding: The portion of the digital-to-analog conversion process that generates an
analog signal value from the digital signal that resulted from analog encoding. (188) Note:
Further action is required to integrate these samples to obtain a continuous approximation of the
original signal, because analog decoding does not smooth the signal.
@@
href="/fs-1037/dir-002/_0287.htm" target="main1">analog encoding
analog encoding: The portion of the analog-to-digital conversion process that samples an analog
signal and creates a digital signal that represents the value of the sample. (188) Note: Multiple
samples are needed to digitize a waveform over a time interval.
@@
href="/fs-1037/dir-002/_0288.htm" target="main1">analog facsimile equipment
analog facsimile equipment: Facsimile equipment in which (a) analog techniques are used to
encode the image detected by the scanner and (b) the output is an analog signal. Note: Examples
of analog facsimile equipment are CCITT Group 1 and CCITT Group 2 facsimile equipment.
@@
href="/fs-1037/dir-002/_0289.htm" target="main1">analog signal
analog signal: 1. A signal that has a continuous nature rather than a pulsed or discrete nature.
Note: Electrical or physical analogies, such as continuously varying voltages, frequencies, or
phases, may be used as analog signals. (188) 2. A nominally continuous electrical signal that
varies in some direct correlation with another signal impressed on a transducer. (188) Note: For
example, an analog signal may vary in frequency, phase, or amplitude in response to changes in
physical phenomena, such as sound, light, heat, position, or pressure.
@@
href="/fs-1037/dir-002/_0290.htm" target="main1">analog switch
analog switch: Switching equipment designed, designated, or used to connect circuits between
users for real-time transmission of analog signals. (188)
@@
href="/fs-1037/dir-002/_0291.htm" target="main1">analog transmission
analog transmission: Transmission of a continuously varying signal as opposed to transmission
of a discretely varying signal.
@@
href="/fs-1037/dir-002/_0292.htm" target="main1">angle modulation
angle modulation: Modulation in which the phase or frequency of a sinusoidal carrier is varied.
(188) Note: Phase and frequency modulation are particular forms of angle modulation.
@@
href="/fs-1037/dir-002/_0293.htm" target="main1">angle of deviation
angle of deviation: In optics, the net angular deflection experienced by a light ray after one or
more refractions or reflections. (188)
@@
href="/fs-1037/dir-002/_0294.htm" target="main1">angle of incidence
angle of incidence: The angle between an incident ray and the normal to a reflecting or refracting
surface. (188)
@@
href="/fs-1037/dir-002/_0295.htm" target="main1">angstrom (
)
angstrom (): A unit of length equal to 10-10 m. Note 1: The angstrom is not an SI (International
System) unit, and it is not accepted for government use (Fed. Std. 376B). Note 2: The angstrom
is, and historically has been, used in the fields of optics, spectroscopy, and microscopy.
@@
href="/fs-1037/dir-002/_0296.htm" target="main1">angular misalignment loss
angular misalignment loss: Power loss caused by the deviation from optimum angular alignment
of the axes of source to waveguide, waveguide to waveguide, or waveguide to detector. Note 1:
The waveguide may be dielectric (an optical fiber) or metallic. Note 2: Angular misalignment
loss does not include lateral offset loss and longitudinal offset loss.
@@
href="/fs-1037/dir-002/_0297.htm" target="main1">ANI
ANI: Abbreviation for automatic number identification.
@@
href="/fs-1037/dir-002/_0298.htm" target="main1">anisochronous
anisochronous: Pertaining to transmission in which the time interval separating any two
significant instants in sequential signals is not necessarily related to the time interval separating
any other two significant instants. Note: Isochronous and anisochronous are characteristics, while
synchronous and asynchronous are relationships.
@@
href="/fs-1037/dir-002/_0299.htm" target="main1"> anisochronous transmission
anisochronous transmission: See asynchronous transmission.
@@
href="/fs-1037/dir-003/_0300.htm" target="main1">anisotropic
anisotropic: Pertaining to a material whose electrical or optical properties vary with (a) the
direction of propagation of a traveling wave or with (b) different polarizations of a traveling
wave. Note 1: Anisotropy is exhibited by non-cubic crystals, which have different refractive
indices for lightwaves propagating in different directions or with different polarizations. Note 2:
Anisotropy may be induced in certain materials under mechanical strain.
@@
href="/fs-1037/dir-003/_0301.htm" target="main1">anomalous propagation (AP)
anomalous propagation (AP): Abnormal propagation caused by fluctuations in the properties
(such as density and refractive index) of the propagation medium. (188) Note: AP may result in
the reception of signals well beyond the distances usually expected.
@@
href="/fs-1037/dir-003/_0302.htm" target="main1">ANS
ANS: Abbreviation for American National Standard.
@@
href="/fs-1037/dir-003/_0303.htm" target="main1">ANSI
ANSI: Abbreviation for American National Standards Institute.
@@
href="/fs-1037/dir-003/_0304.htm" target="main1">ANSI/EIA/TIA-568
ANSI/EIA/TIA-568: A U.S. industry standard that specifies a generic telecommunications
cabling system, which will support a multiproduct, multivendor environment, for commercial
buildings. Note 1: The standard specifies performance characteristics for unshielded twisted pair
telecommunications cabling, including categories allowing data communications up to 100 Mb/s.
These categories are designated 3, 4, and 5. Categories 1 and 2 have not been defined. Note 2:
The standard has been adopted as FIPS PUB 174.
@@
href="/fs-1037/dir-003/_0305.htm" target="main1">answer back
answer back: A signal sent by receiving equipment to the sending station to indicate that the
receiver is ready to accept transmission.
@@
href="/fs-1037/dir-003/_0306.htm" target="main1">answer signal
answer signal: A supervisory signal returned from the called telephone to the originating switch
when the call receiver answers. Note 1: The answer signal stops the ringback signal from being
returned to the caller. Note 2: The answer signal is returned by means of a closed loop.
@@
href="/fs-1037/dir-003/_0307.htm" target="main1">antenna
antenna: Any structure or device used to collect or radiate electromagnetic waves. (188)
@@
href="/fs-1037/dir-003/_0308.htm" target="main1">antenna aperture
antenna aperture: See aperture (def #1).
@@
href="/fs-1037/dir-003/_0309.htm" target="main1">antenna array
antenna array: An assembly of antenna elements with dimensions, spacing, and illumination
sequence such that the fields for the individual elements combine to produce a maximum
intensity in a particular direction and minimum field intensities in other directions.
@@
href="/fs-1037/dir-003/_0310.htm" target="main1">antenna blind cone
antenna blind cone: The volume of space, usually approximately conical with its vertex at the
antenna, that cannot be scanned by an antenna because of limitations of the antenna radiation
pattern and mount. Note: An example of an antenna blind cone is that of an air route
surveillance radar (ARSR). The horizontal radiation pattern of an ARSR antenna is very narrow.
The vertical radiation pattern is fan-shaped, reaching approximately 70° of elevation above
the horizontal plane. As the antenna is rotated about a vertical axis, it can illuminate targets only
if they are 70° or less from the horizontal plane. Above that elevation, they are in the
antenna blind cone. Synonym cone of silence.
@@
href="/fs-1037/dir-003/_0311.htm" target="main1">antenna coupler
antenna coupler: A device used to match the impedance of a transmitter and/or receiver to an
antenna to provide maximum power transfer.
@@
href="/fs-1037/dir-003/_0312.htm" target="main1">antenna dissipative loss
antenna dissipative loss: A power loss resulting from changes in the measurable impedance of a
practical antenna from a value theoretically calculated for a perfect antenna.
@@
href="/fs-1037/dir-003/_0313.htm" target="main1">antenna effective area
antenna effective area: The functionally equivalent area from which an antenna directed toward
the source of the received signal gathers or absorbs the energy of an incident electromagnetic
wave. Note 1: Antenna effective area is usually expressed in square meters. Note 2: In the case
of parabolic and horn-parabolic antennas, the antenna effective area is about 0.35 to 0.55 of the
geometric area of the antenna aperture.
@@
href="/fs-1037/dir-003/_0314.htm" target="main1">antenna efficiency
antenna efficiency: The ratio of the total radiated power to the total input power. Note: The total
radiated power is the total input power less antenna dissipative losses.
@@
href="/fs-1037/dir-003/_0315.htm" target="main1">antenna electrical beam tilt
antenna electrical beam tilt: The shaping of the radiation pattern in the vertical plane of a
transmitting antenna by electrical means so that maximum radiation occurs at an angle below the
horizontal plane. [47CFR]
@@
href="/fs-1037/dir-003/_0316.htm" target="main1">antenna gain-to-noise-temperature (G/T)
antenna gain-to-noise-temperature (G/T): In the characterization of antenna performance, a
figure of merit, where G is the antenna gain in decibels at the receive frequency, and T is the
equivalent noise temperature of the receiving system in kelvins.
@@
href="/fs-1037/dir-003/_0317.htm" target="main1">antenna gain
antenna gain: The ratio of the power required at the input of a loss-free reference antenna to the
power supplied to the input of the given antenna to produce, in a given direction, the same field
strength at the same distance. Note 1: Antenna gain is usually expressed in dB. Note 2: Unless
otherwise specified, the gain refers to the direction of maximum radiation. The gain may be
considered for a specified polarization. Depending on the choice of the reference antenna, a
distinction is made between: absolute or isotropic gain (Gi), when the reference antenna is an
isotropic antenna isolated in space; gain relative to a half-wave dipole (Gd) when the reference
antenna is a half-wave dipole isolated in space and with an equatorial plane that contains the
given direction; gain relative to a short vertical antenna (Gr), when the reference antenna is a
linear conductor, much shorter than one quarter of the wavelength, normal to the surface of a
perfectly conducting plane which contains the given direction. [RR] (188) Synonyms gain of an
antenna, power gain of an antenna.
@@
href="/fs-1037/dir-003/_0318.htm" target="main1">antenna height above average terrain
antenna height above average terrain: The antenna height above the average terrain elevations
from 3.2 to 16 kilometers (2 to 10 miles) from the antenna for the eight directions spaced evenly
for each 45° of azimuth starting with true north. (188) Note: In general, a different
antenna height above average terrain will be determined in each direction from the antenna. The
average of these eight heights is the antenna height above average terrain. In some cases, such as
seashore, fewer than eight directions may be used.
@@
href="/fs-1037/dir-003/_0319.htm" target="main1">antenna lobe
antenna lobe: A three-dimensional section of the radiation pattern of a directional antenna,
bounded by one or more cones of nulls or by regions of diminished irradiance. (188)
@@
href="/fs-1037/dir-003/_0320.htm" target="main1">antenna matching
antenna matching: The process of adjusting impedance so that the input impedance of an
antenna equals or approximates the characteristic impedance of its transmission line over a
specified range of frequencies. (188) Note: The impedance of either the transmission line, or the
antenna, or both, may be adjusted to effect the match.
@@
href="/fs-1037/dir-003/_0321.htm" target="main1">antenna noise temperature
antenna noise temperature: The temperature of a hypothetical resistor at the input of an ideal
noise-free receiver that would generate the same output noise power per unit bandwidth as that at
the antenna output at a specified frequency. (188) Note 1: The antenna noise temperature
depends on antenna coupling to all noise sources in its environment as well as on noise generated
within the antenna. Note 2: The antenna noise temperature is a measure of noise whose value is
equal to the actual temperature of a passive device.
@@
href="/fs-1037/dir-003/_0322.htm" target="main1">anti-clockwise polarized wave
anti-clockwise polarized wave: Synonym left-hand polarized wave.
@@
href="/fs-1037/dir-003/_0323.htm" target="main1">anti-interference
anti-interference: Pertaining to equipment, processes, or techniques used to reduce the effect of
natural and man-made noise on radio communications.
@@
href="/fs-1037/dir-003/_0324.htm" target="main1">anti-jam
anti-jam: Measures to ensure that intended transmitted information can be received despite
deliberate jamming attempts. [NIS] (188)
@@
href="/fs-1037/dir-003/_0325.htm" target="main1">anti-node
anti-node: A point in a standing wave at which the amplitude is a maximum.
@@
href="/fs-1037/dir-003/_0326.htm" target="main1">anti-spoof
anti-spoof: Measures to prevent an opponent's participation in a telecommunications network, or
operation/control of a cryptographic or COMSEC system. [NIS]
@@
href="/fs-1037/dir-003/_0327.htm" target="main1">antireflection coating
antireflection coating: A thin, dielectric or metallic film, or several such films, applied to an
optical surface to reduce its reflectance and thereby increase its transmittance. [After 2196] Note:
For minimum reflection of a normal incident wave of a single wavelength, the antireflection
coating may consist of a single layer and must have (a) a refractive index equal to the square root
of the refractive indices of the materials bounding the coating, and (b) a thickness equal to
one-quarter the wavelength in question (i.e. , the wavelength within the material of which the
coating consists). For minimum reflection of multiple wavelengths, additional layers must be
added.
@@
href="/fs-1037/dir-003/_0328.htm" target="main1">anycall
anycall: In adaptive high-frequency (HF) radio automatic link establishment, a broadcast in
which (a) the called stations are unspecified, (b) stations receiving the call stop scanning, and (c)
each station automatically responds in pseudorandom time slots. (188)
@@
href="/fs-1037/dir-003/_0329.htm" target="main1">AP
AP: Abbreviation for anomalous propagation.
@@
href="/fs-1037/dir-003/_0330.htm" target="main1">APC
APC: Abbreviation for adaptive predictive coding.
@@
href="/fs-1037/dir-003/_0331.htm" target="main1">APD
APD: Abbreviation for avalanche photodiode . Note: apd and a.p.d. are also used.
@@
href="/fs-1037/dir-003/_0332.htm" target="main1">aperiodic antenna
aperiodic antenna: An antenna designed to have an approximately constant input impedance
over a wide range of frequencies. Note: Examples of aperiodic antennas include terminated
rhombic antennas and wave antennas. Synonym nonresonant antenna.
@@
href="/fs-1037/dir-003/_0333.htm" target="main1">aperture-to-medium coupling loss
aperture-to-medium coupling loss: The difference between the theoretical gain of a very large
antenna, such as the antennas in beyond-the-horizon microwave links, and the gain that can be
realized in operation. Note 1: Aperture-to-medium coupling loss is related to the ratio of the
scatter angle to the antenna beamwidth. Note 2: The "very large antennas" are referred to in
wavelengths; thus, this loss can apply to line-of-sight systems also. (188)
@@
href="/fs-1037/dir-003/_0334.htm" target="main1">aperture
aperture: 1. In a directional antenna, the portion of a plane surface very near the antenna normal
to the direction of maximum radiant intensity, through which the major part of the radiation
passes. (188) 2. In an acoustic device that launches a sound wave, the passageway, determined
by the size of a hole in the inelastic material and the wavelength. [After 2196]
@@
href="/fs-1037/dir-003/_0335.htm" target="main1">aperture distortion
aperture distortion: In facsimile, the distortion of the recorded image caused by the shape and
finite size of the scanning and recording apertures. Note: The distortion may occur in one or
more attributes of the recorded image, such as in resolution, density, or shape.
@@
href="/fs-1037/dir-003/_0336.htm" target="main1">aperture illumination
aperture illumination: 1. The field distribution, in amplitude and phase, over the antenna
physical aperture. 2. The phase and amplitude of the element feed voltages or the distribution of
the currents in an array of elements.
@@
href="/fs-1037/dir-003/_0337.htm" target="main1">API
API: Abbreviation for application program interface.
@@
href="/fs-1037/dir-003/_0338.htm" target="main1">apogee
apogee: In an orbit of a satellite orbiting the Earth, the point that is farthest from the
gravitational center of the Earth.
@@
href="/fs-1037/dir-003/_0339.htm" target="main1">apogee altitude
apogee altitude: See altitude of the apogee or of the perigee .
@@
href="/fs-1037/dir-003/_0340.htm" target="main1">apparent power
apparent power: In alternating-current power transmission and distribution, the product of the
rms voltage and amperage. Note 1: When the applied voltage and the current are in phase with
one another, the apparent power is equal to the effective power, i.e., the real power delivered to
or consumed by the load. If the current lags or leads the applied voltage, the apparent power is
greater than the effective power. Note 2: Only effective power, i.e., the real power delivered to
or consumed by the load, is expressed in watts. Apparent power is properly expressed only in
volt-amperes, never watts. See diagram under effective power.
@@
href="/fs-1037/dir-003/_0341.htm" target="main1">Application Layer
Application Layer: See Open Systems Interconnection--Reference Model.
@@
href="/fs-1037/dir-003/_0342.htm" target="main1">application program interface (API)
application program interface (API): A formalized set of software calls and routines that can be
referenced by an application program in order to access supporting network services.
@@
href="/fs-1037/dir-003/_0343.htm" target="main1">applique
applique: Circuit components added to an existing system to provide additional or alternate
functions. (188) Note: Applique may be used to modify carrier telephone equipment designed
for ringdown manual operation to allow for use between points having dial equipment.
@@
href="/fs-1037/dir-003/_0344.htm" target="main1">approved circuit
approved circuit: Deprecated synonym for protected distribution system.
@@
href="/fs-1037/dir-003/_0345.htm" target="main1">aramid yarn
aramid yarn: Generic name for a tough synthetic yarn that is often used in optical cable
construction for the strength member, protective braid, and/or rip cord for jacket removal. [FAA]
@@
href="/fs-1037/dir-003/_0346.htm" target="main1">Archie
Archie: Distributed-system-based software that searches indices of files available on public
servers on the Internet. Note 1: Archie servers may provide access via telnet, E-mail, or a
special Archie client. Note 2: Using Archie requires a user to be familiar with where the indices
are located, i.e. , the user must provide an Archie server domain name or IP address.
@@
href="/fs-1037/dir-003/_0347.htm" target="main1">architecture
architecture: See computer architecture, network architecture.
@@
href="/fs-1037/dir-003/_0348.htm" target="main1">archiving
archiving: The storing of files, records, and other data for reference and alternative backup.
@@
href="/fs-1037/dir-003/_0349.htm" target="main1">area broadcast shift
area broadcast shift: The changing from listening to transmissions intended for one broadcast
area to listening to transmissions intended for another broadcast area. Note 1: An area broadcast
shift may occur when a ship or aircraft crosses the boundary between listening areas. Note 2:
Shift times, on the date a ship or aircraft is expected to pass into another area, must be strictly
observed or the ship or aircraft will miss messages intended for it. Synonym radio watch shift.
@@
href="/fs-1037/dir-003/_0350.htm" target="main1">area code
area code: See access code, code, country code, NXX code.
@@
href="/fs-1037/dir-003/_0351.htm" target="main1">area loss
area loss: When optical fibers are joined by a splice or a pair of mated connectors, a power loss
that is caused by any mismatch in size or shape of the cross section of the cores of the mating
fibers. Note 1: Any of the above conditions may allow light from the core of the "transmitting"
fiber to enter the cladding of the "receiving" fiber, where it is quickly lost. Note 2: Area loss may
be dependent on the direction of propagation. For example, in coupling a signal from an optical
fiber having a smaller core to an otherwise identical one having a larger core, there will be no
area loss, but in the opposite direction, there will be area loss. [After FAA]
@@
href="/fs-1037/dir-003/_0352.htm" target="main1">argument
argument: 1. An independent variable. 2. Any value of an independent variable. Note:
Examples of arguments include search keys, numbers that identify the location of a data item in a
table, and the in sin .
@@
href="/fs-1037/dir-003/_0353.htm" target="main1">arithmetic and logic unit (ALU)
arithmetic and logic unit (ALU): A part of a computer that performs arithmetic, logic, and
related operations.
@@
href="/fs-1037/dir-003/_0354.htm" target="main1">arithmetic overflow
arithmetic overflow: 1. In a digital computer, the condition that occurs when a calculation
produces a result that is greater than a given register or storage location can store or represent.
(188) 2. In a digital computer, the amount that a calculated value is greater than a given register
or storage location can store or represent. Note: The overflow may be placed at another location.
(188) Synonym overflow.
@@
href="/fs-1037/dir-003/_0355.htm" target="main1">arithmetic register
arithmetic register: A register that holds the operands or the results of operations such as
arithmetic operations, logic operations, and shifts.
@@
href="/fs-1037/dir-003/_0356.htm" target="main1">arithmetic shift
arithmetic shift: A shift, applied to the representation of a number in a fixed radix numeration
system and in a fixed-point representation system, and in which only the characters representing
the fixed-point part of the number are moved. An arithmetic shift is usually equivalent to
multiplying the number by a positive or a negative integral power of the radix, except for the
effect of any rounding; compare the logical shift with the arithmetic shift, especially in the case
of floating-point representation.
@@
href="/fs-1037/dir-003/_0357.htm" target="main1">arithmetic underflow
arithmetic underflow: In a digital computer, the condition that occurs when a calculation
produces a non-zero result that is less than the smallest non-zero quantity that a given register or
storage location can store or represent.
@@
href="/fs-1037/dir-003/_0358.htm" target="main1">arithmetic unit
arithmetic unit: In a processor, the part that performs arithmetic operations; sometimes the unit
performs both arithmetic and logic operations.
@@
href="/fs-1037/dir-003/_0359.htm" target="main1">Armed Forces Radio Service (AFRS)
Armed Forces Radio Service (AFRS): A radio broadcasting service that is operated by and for
the personnel of the armed services in the area covered by the broadcast. Note: An example of
an AFRS is the radio service operated by the U.S. Army for U.S. and allied military personnel on
duty in overseas areas.
@@
href="/fs-1037/dir-003/_0360.htm" target="main1">armor
armor: Of a communications cable, a component intended to protect the critical internal
components, e.g., buffer tubes or fibers, or electrical conductors, from damage from external
mechanical attack, e.g., rodent attack or abrasion. [After FAA] Note: Armor usually takes the
form of a steel or aluminum tape wrapped about an inner jacket that covers the critical internal
components. An outer jacket usually covers the armor.
@@
href="/fs-1037/dir-003/_0361.htm" target="main1">ARP
ARP: Abbreviation for address resolution protocol.
@@
href="/fs-1037/dir-003/_0362.htm" target="main1">ARPANET
ARPANET: Abbreviation for Advanced Research Projects Agency Network. A
packet-switching network used by the Department of Defense, later evolved into the Internet.
@@
href="/fs-1037/dir-003/_0363.htm" target="main1">ARQ
ARQ: Abbreviation for automatic repeat-request. Error control for data transmission in which
the receiver detects transmission errors in a message and automatically requests a retransmission
from the transmitter. Note: Usually, when the transmitter receives the ARQ, the transmitter
retransmits the message until it is either correctly received or the error persists beyond a
predetermined number of retransmissions. (188) Synonyms error-detecting-and-feedback
system, repeat-request system.
@@
href="/fs-1037/dir-003/_0364.htm" target="main1">array
array: 1. An arrangement of elements in one or more dimensions. 2. In a programming language,
an aggregate that consists of data objects with identical attributes, each of which may be uniquely
referenced by subscription.
@@
href="/fs-1037/dir-003/_0365.htm" target="main1">array processor
array processor: A processor capable of executing instructions in which the operands may be
arrays rather than data elements. Synonym vector processor .
@@
href="/fs-1037/dir-003/_0366.htm" target="main1">arrester
arrester: A device that protects hardware, such as systems, subsystems, circuits, and equipment,
from voltage or current surges produced by lightning or electromagnetic pulses. Note: If the
hardware is adequately protected, associated software may also be adequately protected. (188)
Synonym surge suppressor.
@@
href="/fs-1037/dir-003/_0367.htm" target="main1">ARS
ARS: Abbreviation for automatic route selection.
@@
href="/fs-1037/dir-003/_0368.htm" target="main1">art line
art line: Colloquial synonym for artificial transmission line.
@@
href="/fs-1037/dir-003/_0369.htm" target="main1">articulation index
articulation index: A measure of the intelligibility of voice signals, expressed as a percentage of
speech units that are understood by the listener when heard out of context. (188) Note: The
articulation index is affected by noise, interference, and distortion.
@@
href="/fs-1037/dir-003/_0370.htm" target="main1">articulation score (AS)
articulation score (AS): A subjective measure of the intelligibility of a voice system in terms of
the percentage of words correctly understood over a channel perturbed by interference. Note:
Articulation scores have been experimentally obtained as functions of varying word content,
bandwidth, audio signal-to-noise ratio and the experience of the talkers and listeners involved.
@@
href="/fs-1037/dir-003/_0371.htm" target="main1">artificial intelligence (AI)
artificial intelligence (AI): The capability of a device to perform functions that are normally
associated with human intelligence, such as reasoning and optimization through experience.
Note: AI is the branch of computer science that attempts to approximate the results of human
reasoning by organizing and manipulating factual and heuristic knowledge. Areas of AI activity
include expert systems, natural language understanding, speech recognition, vision, and robotics.
@@
href="/fs-1037/dir-003/_0372.htm" target="main1">artificial transmission line
artificial transmission line: A four-terminal electrical network, i.e. an electrical circuit, that has
the characteristic impedance, transmission time delay, phase shift, and/or other parameter(s) of a
real transmission line and therefore can be used to simulate a real transmission line in one or
more of these respects. Colloquial synonym art line.
@@
href="/fs-1037/dir-003/_0373.htm" target="main1">ARU
ARU: Abbreviation fo r audio response unit.
@@
href="/fs-1037/dir-003/_0374.htm" target="main1">ASCII
ASCII: Acronym for American Standard Code for Information Interchange. The standard code
used for information interchange among data processing systems, data communications systems,
and associated equipment in the United States. (188) Note 1: The ASCII character set contains
128 coded characters. Note 2: Each ASCII character is a 7-bit coded unique character; 8 bits
when a parity check bit is included. Note 3: The ASCII character set consists of control
characters and graphic characters. Note 4: When considered simply as a set of 128 unique bit
patterns, or 256 with a parity bit, disassociated from the character equivalences in national
implementations, the ASCII may be considered as an alphabet used in machine languages. Note
5: The ASCII is the U.S. implementation of International Alphabet No. 5 (IA No. 5) as specified
in CCITT Recommendation V.3.
@@
href="/fs-1037/dir-003/_0375.htm" target="main1">ASP
ASP: Abbreviation for adjunct service point.
@@
href="/fs-1037/dir-003/_0376.htm" target="main1">aspect ratio
aspect ratio: In facsimile or television, the ratio of the width to the height of a picture, document,
or scanning field.
@@
href="/fs-1037/dir-003/_0377.htm" target="main1">assemble
assemble: To translate a computer program expressed in an assembly language into a machine
language.
@@
href="/fs-1037/dir-003/_0378.htm" target="main1">assembler
assembler: A computer program that is used to assemble. Synonym assembly program.
@@
href="/fs-1037/dir-003/_0379.htm" target="main1">assembly
assembly: In logistics, an item forming a portion of an equipment that can be provisioned and
replaced as an entity and which normally incorporates replaceable parts or groups of parts. [JP1]
@@
href="/fs-1037/dir-003/_0380.htm" target="main1">assembly language
assembly language: A computer-oriented language (a) in which instructions are symbolic and
usually in one-to-one correspondence with sets of machine language instructions and (b) that may
provide other facilities, such as the use of macro instructions. (188) Synonym
computer-dependent language.
@@
href="/fs-1037/dir-003/_0381.htm" target="main1">assembly program
assembly program: Synonym assembler.
@@
href="/fs-1037/dir-003/_0382.htm" target="main1">assembly time
assembly time: The elapsed time taken for the execution of an assembler.
@@
href="/fs-1037/dir-003/_0383.htm" target="main1">assigned frequency
assigned frequency: 1. The center of the assigned frequency band assigned to a station. [RR] 2.
The frequency of the center of the radiated bandwidth. (188) Note: The frequency of the rf
carrier, whether suppressed or radiated, is usually given in parentheses following the assigned
frequency, and is the frequency appearing in the dial settings of rf equipment intended for
single-sideband or independent-sideband transmission.
@@
href="/fs-1037/dir-003/_0384.htm" target="main1">assigned frequency band
assigned frequency band: The frequency band within which the emission of a station is
authorized; the width of the band equals the necessary bandwidth plus twice the absolute value of
the frequency tolerance. Where space stations are concerned, the assigned frequency band
includes twice the maximum Doppler shift that may occur in relation to any point of the Earth's
surface. [NTIA] [RR]
@@
href="/fs-1037/dir-003/_0385.htm" target="main1">assignment (of a radio frequency or radio
frequency channel)
assignment (of a radio frequency or radio frequency channel): Authorization given by an
administration for a radio station to use a radio frequency or radio frequency channel under
specified conditions. [NTIA] [RR]
@@
href="/fs-1037/dir-003/_0386.htm" target="main1">assignment
assignment: For NS/EP, the designation of priority level(s).
@@
href="/fs-1037/dir-003/_0387.htm" target="main1">associated common-channel signaling
associated common-channel signaling: Common-channel signaling in which the signal channel
is associated with a specific trunk group and terminates at the same pair of switches as the trunk
group. (188) Note: In associated common-channel signaling, the signaling is usually
accomplished by using the same facilities as the associated trunk group.
@@
href="/fs-1037/dir-003/_0388.htm" target="main1">associative storage
associative storage: 1. A storage device whose storage locations are identified by their contents,
or by a part of their contents, rather than by their names or positions. Note: Associative storage
can also refer to this process as well as to the device. Synonym content-addressable storage. 2.
Storage that supplements another storage.
@@
href="/fs-1037/dir-003/_0389.htm" target="main1">asymmetrical modulator
asymmetrical modulator: Synonym unbalanced modulator.
@@
href="/fs-1037/dir-003/_0390.htm" target="main1">asynchronous communications system
asynchronous communications system: A data communications system that uses asynchronous
operation. Note 1: In an asynchronous communications system, extra signal elements are usually
appended to the data for the purpose of synchronizing individual data characters or blocks. (188)
Note 2: The time spacing between successive data characters or blocks may be of arbitrary
duration. Synonym start-stop system.
@@
href="/fs-1037/dir-003/_0391.htm" target="main1">asynchronous network
asynchronous network: A network in which the clocks do not need to be synchronous or
mesochronous. (188) Synonym nonsynchronous network.
@@
href="/fs-1037/dir-003/_0392.htm" target="main1">asynchronous operation
asynchronous operation: 1. A sequence of operations in which operations are executed out of
time coincidence with any event. (188) 2. An operation that occurs without a regular or
predictable time relationship to a specified event; e.g., the calling of an error diagnostic routine
that may receive control at any time during the execution of a computer program. (188) Synonym
asynchronous working.
@@
href="/fs-1037/dir-003/_0393.htm" target="main1">asynchronous time-division multiplexing
(ATDM)
asynchronous time-division multiplexing (ATDM): Time-division multiplexing in which
asynchronous transmission is used.
@@
href="/fs-1037/dir-003/_0394.htm" target="main1">asynchronous transfer mode (ATM)
asynchronous transfer mode (ATM): A high-speed multiplexing and switching method utilizing
fixed-length cells of 53 octects to support multiple types of traffic. Note: ATM, specified in
international standards, is asynchronous in the sense that cells carrying user data need not be
periodic.
@@
href="/fs-1037/dir-003/_0395.htm" target="main1">asynchronous transmission
asynchronous transmission: Data transmission in which the instant that each character, or block
of characters, starts is arbitrary; once started, the time of occurrence of each signal representing a
bit within the character, or block, has the same relationship to significant instants of a fixed time
frame. (188)
@@
href="/fs-1037/dir-003/_0396.htm" target="main1">asynchronous working
asynchronous working: Synonym asynchronous operation.
@@
href="/fs-1037/dir-003/_0397.htm" target="main1">AT Commands
AT Commands: A de facto standard for modem commands from an attached CPU, used in most
1,200 and 2,400 b/s modems.
@@
href="/fs-1037/dir-003/_0398.htm" target="main1">ATB
ATB: Abbreviation for all trunks busy.
@@
href="/fs-1037/dir-003/_0399.htm" target="main1">ATDM
ATDM: Abbreviation for asynchronous time-division multiplexing.
@@
href="/fs-1037/dir-003/_0400.htm" target="main1">ATM
ATM: Abbreviation for asynchronous transfer mode.
@@
href="/fs-1037/dir-003/_0401.htm" target="main1">atmospheric duct
atmospheric duct: A horizontal layer in the lower atmosphere in which the vertical refractive
index gradients are such that radio signals (a) are guided or focused within the duct, (b) tend to
follow the curvature of the Earth, and (c) experience less attenuation in the ducts than they would
if the ducts were not present. (188) Note: The reduced refractive index at the higher altitudes
bends the signals back toward the Earth. Signals in a higher refractive index layer, i.e., duct, tend
to remain in that layer because of the reflection and refraction encountered at the boundary with a
lower refractive index material.
@@
href="/fs-1037/dir-003/_0402.htm" target="main1">atmospheric noise
atmospheric noise: Radio noise caused by natural atmospheric processes, primarily lightning
discharges in thunderstorms. (188)
@@
href="/fs-1037/dir-003/_0403.htm" target="main1">atomic time
atomic time: See International Atomic Time.
@@
href="/fs-1037/dir-003/_0404.htm" target="main1">ATOW
ATOW: Acronym for acquisition and tracking orderwire . A downlink circuit that provides a
terminal with information regarding uplink acquisition and synchronization status. (188)
@@
href="/fs-1037/dir-003/_0405.htm" target="main1">attachment unit interface (AUI)
attachment unit interface (AUI): In a local area network, the interface between the medium
access unit (MAU) and the data terminal equipment within a data station.
@@
href="/fs-1037/dir-003/_0406.htm" target="main1">attack time
attack time: The time between (a) the instant that a signal at the input of a device or circuit
exceeds the activation threshold of the device or circuit and (b) the instant that the device or
circuit reacts in a specified manner, or to a specified degree, to the input. Note: Attack time
occurs in devices such as clippers, peak limiters, compressors, and voxes.
@@
href="/fs-1037/dir-003/_0407.htm" target="main1">attendant access loop
attendant access loop: A switched circuit that provides an attendant with a manual means for call
completion and control. Note: An attendant access loop might be given a specific telephone
number.
@@
href="/fs-1037/dir-003/_0408.htm" target="main1">attendant conference
attendant conference: A network-provided service feature that allows an attendant to establish a
conference connection of three or more users.
@@
href="/fs-1037/dir-003/_0409.htm" target="main1">attendant position
attendant position: The part of a switching system used by an attendant, i.e., an operator, to
assist users in call completion and use of special services. (188)
@@
href="/fs-1037/dir-003/_0410.htm" target="main1">attention signal
attention signal: The attention signal to be used by AM, FM, and TV broadcast stations to
actuate muted receivers for inter-station receipt of emergency cuing announcements and
broadcasts involving a range of emergency contingencies posing a threat to the safety of life or
property. [47CFR]
@@
href="/fs-1037/dir-003/_0411.htm" target="main1">attenuation-limited operation
attenuation-limited operation: The condition that prevails when attenuation, rather than
bandwidth, limits the performance of a communications link. (188)
@@
href="/fs-1037/dir-003/_0412.htm" target="main1">attenuation
attenuation: The decrease in intensity of a signal, beam, or wave as a result of absorption of
energy and of scattering out of the path to the detector, but not including the reduction due to
geometric spreading. [After JP1] Note 1: Attenuation is usually expressed in dB. Note 2:
"Attenuation" is often used as a misnomer for "attenuation coefficient, " which is expressed in
dB per kilometer. Note 3: A distinction must be made as to whether the attenuation is that of
signal power or signal electric field strength.
@@
href="/fs-1037/dir-003/_0413.htm" target="main1">attenuation coefficient
attenuation coefficient: The rate of diminution of average power with respect to distance along a
transmission path. Synonym attenuation rate.
@@
href="/fs-1037/dir-003/_0414.htm" target="main1">attenuation constant
attenuation constant: 1. The real part of the propagation constant in any electromagnetic
propagation medium. Note 1: The attenuation constant is usually expressed as a numerical value
per unit length. Note 2: The attenuation constant may be calculated or experimentally
determined for each medium. 2. For a particular propagation mode in an optical fiber, the real
part of the axial propagation constant.
@@
href="/fs-1037/dir-003/_0415.htm" target="main1">attenuation rate
attenuation rate: Synonym attenuation coefficient.
@@
href="/fs-1037/dir-003/_0416.htm" target="main1">attenuator
attenuator: 1. In electrical systems, a network that reduces the amplitude of a signal without
appreciably distorting its waveform. Note 1: Electrical attenuators are usually passive devices.
Note 2: The degree of attenuation may be fixed, continuously adjustable, or incrementally
adjustable. Fixed attenuators are often called pads, especially in telephony. Note 3: The input
and output impedances of an attenuator are usually matched to the impedances of the signal
source and load, respectively. 2. In optical systems, a device that reduces the amplitude of a
signal without appreciably distorting its waveform. Note 1: Optical attenuators are usually
passive devices. Note 2: The degree of attenuation may be fixed, continuously adjustable, or
incrementally adjustable.
@@
href="/fs-1037/dir-003/_0417.htm" target="main1">attribute
attribute: 1. In database management, a property inherent in an entity or associated with that
entity for database purposes. (188) 2. In network management, a property of a managed object
that has a value. (188) Note 1: Mandatory initial values for attributes can be specified as part of
the managed object class definition. Note 2: Attributes may be either mandatory or conditional.
@@
href="/fs-1037/dir-003/_0418.htm" target="main1">ATV
ATV: Abbreviation for advanced television.
@@
href="/fs-1037/dir-003/_0419.htm" target="main1">audible
audible: Synonym for audible ringing tone.
@@
href="/fs-1037/dir-003/_0420.htm" target="main1">audible ringing tone
audible ringing tone: In telephony, a signal, usually consisting of an audio tone interrupted at a
slow repetition rate, provided to a caller to indicate that the called-party instrument is being sent
a ringing signal. (188) Note: The audible ringing tone may be generated by the called-party
servicing switch or by the calling-party servicing switch, but it is not generated by the called
telephone instrument. Synonyms audible, ringback tone.
@@
href="/fs-1037/dir-003/_0421.htm" target="main1">audio frequency (AF)
audio frequency (AF): The band of frequencies (approximately 20 Hz to 20 kHz) that, when
transmitted as acoustic waves, can be heard by the normal human ear. (188)
@@
href="/fs-1037/dir-003/_0422.htm" target="main1">audio response unit (ARU)
audio response unit (ARU): A device that provides synthesized voice responses to dual-tone
multifrequency signaling input by processing calls based on (a) the call-originator input, (b)
information received from a host data base, and (c) information in the incoming call, such as the
time of day. Note: ARUs are used to increase the number of information calls handled and to
provide consistent quality in information retrieval.
@@
href="/fs-1037/dir-003/_0423.htm" target="main1">audit
audit: 1. To conduct an independent review and examination of system records and activities in
order to test the adequacy and effectiveness of data security and data integrity procedures, to
ensure compliance with established policy and operational procedures, and to recommend any
necessary changes. 2. Independent review and examination of records and activities to assess the
adequacy of system controls, to ensure compliance with established policies and operational
procedures, and to recommend necessary changes in controls, policies, or procedures. [NIS]
@@
href="/fs-1037/dir-003/_0424.htm" target="main1">audit review file
audit review file: A file created by executing statements included in a computer program for the
explicit purpose of providing data for auditing.
@@
href="/fs-1037/dir-003/_0425.htm" target="main1">audit trail
audit trail: 1. A record of both completed and attempted accesses and service. 2. Data in the
form of a logical path linking a sequence of events, used to trace the transactions that have
affected the contents of a record. 3. [In INFOSEC, a] chronological record of system activities to
enable the reconstruction and examination of the sequence of events and/or changes in an event.
Note: Audit trail may apply to information in an AIS, or to the transfer of COMSEC material.
[NIS]
@@
href="/fs-1037/dir-003/_0426.htm" target="main1">AUI
AUI: Abbreviation for attachment unit interface .
@@
href="/fs-1037/dir-003/_0427.htm" target="main1">aurora
aurora: Sporadic radiant emission from the upper atmosphere that usually occurs about the North
and South magnetic poles of the Earth. Note 1: Auroras are most intense at times of intense
magnetic storms caused by sunspot activity. The distribution of auroral intensity with altitude
shows a pronounced maximum near 100 km above the Earth. Auroras may occasionally be
observed within 40° or less of the equator. Note 2: Auroras interfere with radio
communications. Note 3: In the Northern hemisphere, the aurora is called the Aurora Borealis
(Northern Lights). In the Southern hemisphere, the aurora is called the Aurora Australis
(Southern Lights).
@@
href="/fs-1037/dir-003/_0428.htm" target="main1">authenticate
authenticate: 1. To establish, usually by challenge and response, that a transmission attempt is
authorized and valid. 2. Verify the identity of a user, user device, or other entity, or the integrity
of data stored, transmitted, or otherwise exposed to unauthorized modification in an automated
information system, or establish the validity of a transmitted message. [NIS] 3. A challenge
given by voice or electrical means to attest to the authenticity of a message or transmission. [JP1]
@@
href="/fs-1037/dir-003/_0429.htm" target="main1">authentication
authentication: [Any] Security measure designed to establish the validity of a transmission,
message, or originator, or a means of verifying an individual's eligibility to receive specific
categories of information. [NIS]
@@
href="/fs-1037/dir-003/_0430.htm" target="main1">authenticator
authenticator: 1. A symbol or group of symbols, or a series of bits, selected or derived in a
prearranged manner and usually inserted at a predetermined point within a message or
transmission for the purpose of attesting to the validity of the message or transmission. [JP1] 2.
A letter, numeral, group of letters or numerals, or any combinations of these, attesting to the
authenticity of a message or transmission. [After JP1] 3. [In INFOSEC,] means used to confirm
the identity or eligibility of a station, originator, or individual. [NIS]
@@
href="/fs-1037/dir-003/_0431.htm" target="main1">authorization
authorization: 1. The rights granted to a user to access, read, modify, insert, or delete certain
data, or to execute certain programs. 2. Access rights granted to a user, program, or process.
[NIS]
@@
href="/fs-1037/dir-003/_0432.htm" target="main1">authorized bandwidth
authorized bandwidth: Authorized bandwidth is, for purposes of this Manual, the necessary
bandwidth (bandwidth required for transmission and reception of intelligence) and does not
include allowance for transmitter drift or Doppler shift. [NTIA]
@@
href="/fs-1037/dir-003/_0433.htm" target="main1">authorized frequency
authorized frequency: A frequency that is allocated and assigned by a competent authority to a
specific user for a specific purpose. (188) See assigned frequency.
@@
href="/fs-1037/dir-003/_0434.htm" target="main1">AUTODIN
AUTODIN: Acronym for automatic digital network. See Defense Data Network.
@@
href="/fs-1037/dir-003/_0435.htm" target="main1">automated data medium
automated data medium: Synonym machine-readable medium.
@@
href="/fs-1037/dir-003/_0436.htm" target="main1">automated information system (AIS)
automated information system (AIS): 1. An assembly of computer hardware, software, firmware,
or any combination of these, configured to accomplish specific information-handling operations,
such as communication, computation, dissemination, processing, and storage of information. 2.
[In INFOSEC,] any equipment or interconnected system or subsystems of equipment that is used
in the automatic acquisition, storage, manipulation, management, movement, control, display,
switching, interchange, transmission or reception of data and includes computer software,
firmware, and hardware. Note: Included are computers, word processing systems, networks, or
other electronic information handling systems, and associated equipment. [NIS]
@@
href="/fs-1037/dir-003/_0437.htm" target="main1">automated information systems security
automated information systems security: 1. Measures and controls that ensure confidentiality,
integrity, and availability of the information processed and stored by automated information
systems. Note 1: The unauthorized disclosure, modification, or destruction may be accidental or
intentional. Note 2: Automated information systems security includes consideration of all
hardware and software functions, characteristics and features; operational procedures;
accountability procedures; and access controls at the central computer facility, remote computer,
and terminal facilities; management constraints; physical structures and devices, such as
computers, transmission lines, and power sources; and personnel and communications controls
needed to provide an acceptable level of risk for the automated information system and for the
data and information contained in the system. Automated information systems security also
includes the totality of security safeguards needed to provide an acceptable protection level for an
automated information system and for the data handled by an automated information system. 2.
In INFOSEC, synonym computer security .
@@
href="/fs-1037/dir-003/_0438.htm" target="main1">automated maritime telecommunications
system (AMTS)
automated maritime telecommunications system (AMTS): An automatic, integrated and
interconnected maritime communications system serving ship stations on specified inland and
coastal waters of the United States. [47CFR]
@@
href="/fs-1037/dir-003/_0439.htm" target="main1">automated radio
automated radio: A radio that can be automatically controlled by electronic devices and that
requires little or no human intervention.
@@
href="/fs-1037/dir-003/_0440.htm" target="main1">automated tactical command and control
system
automated tactical command and control system: A command and control system, or part
thereof, that manipulates the movement of information from source to user without human
intervention. Note: In an automated tactical command and control system, automated execution
of a decision without human intervention is not mandatory.
@@
href="/fs-1037/dir-003/_0441.htm" target="main1">automatic answering
automatic answering: A service feature in which the called terminal automatically responds to
the calling signal and the call may be established whether or not the called terminal is attended by
an operator.
@@
href="/fs-1037/dir-003/_0442.htm" target="main1">automatic call distributor (ACD)
automatic call distributor (ACD): A device that distributes incoming calls to a specific group of
terminals. Note: If the number of active calls is less than the number of terminals, the next call
will be routed to the terminal that has been in the idle state the longest. If all terminals are busy,
the incoming calls are held in a first-in-first-out queue until a terminal becomes available. (188)
@@
href="/fs-1037/dir-003/_0443.htm" target="main1">automatic callback
automatic callback: A service feature that permits a user, when encountering a busy condition, to
instruct the system to retain the called and calling numbers and to establish the call when there is
an available line. Note 1: Automatic callback may be implemented in the terminal, in the
switching system, or shared between them. Note 2: Automatic callback is not the same as
camp-on.
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href="/fs-1037/dir-003/_0444.htm" target="main1">automatic calling
automatic calling: Calling in which the elements of the selection signal are entered into the data
network contiguously at the full data signaling rate. The selection signal is generated by the data
terminal equipment. Note: A limit may be imposed by the design criteria of the network to
prevent more than a permitted number of unsuccessful call attempts to the same address within a
specified period.
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href="/fs-1037/dir-003/_0445.htm" target="main1">automatic calling unit (ACU)
automatic calling unit (ACU): A device that enables equipment, such as computers and card
dialers, to originate calls automatically over a telecommunications network.
@@
href="/fs-1037/dir-003/_0446.htm" target="main1">automatic data handling (ADH)
automatic data handling (ADH): 1. A generalization of automatic data processing to include the
aspect of data transfer. [JP1] 2. Combining data processing and data transfer.
@@
href="/fs-1037/dir-003/_0447.htm" target="main1">automatic data processing (ADP)
automatic data processing (ADP): 1. An interacting assembly of procedures, processes, methods,
personnel, and equipment to perform automatically a series of data processing operations on data.
Note: The data processing operations may result in a change in the semantic content of the data.
(188) 2. Data processing by means of one or more devices that use common storage for all or
part of a computer program, and also for all or part of the data necessary for execution of the
program; that execute user-written or user-designated programs; that perform user-designated
symbol manipulation, such as arithmetic operations, logic operation, or character-string
manipulations; and that can execute programs that modify themselves during their execution.
Note: Automatic data processing may be performed by a stand-alone unit or by several
connected units. 3. Data processing largely performed by automatic means. [JP1] 4. That branch
of science and technology concerned with methods and techniques relating to data processing
largely performed by automatic means. [JP1]
@@
href="/fs-1037/dir-003/_0448.htm" target="main1">automatic data processing equipment
(ADPE)
automatic data processing equipment (ADPE): Any equipment or interconnected system or
subsystems of equipment that is used in the automatic acquisition, storage, manipulation,
management, movement, control, display, switching, interchange, transmission, or reception, of
data or information (i) by a Federal agency, or (ii) under a contract with a Federal agency which
(i) requires the use of such equipment, or (ii) requires the performance of a service or the
furnishing of a product which is performed or produced making significant use of such
equipment. Such term includes (i) computer, (ii) ancillary equipment, (iii) software, firmware,
and similar procedures, (iv) services, including support services, and (v) related resources as
defined by regulations issued by the Administrator for General Services. . . . [Public Law 99-500,
Title VII, Sec. 822 (a) Section 111(a) of the Federal Property and Administrative Services Act of
1949 (40 U.S.C. 759(a)) revised. ] See also paragraph #3 of the Foreword above.
@@
href="/fs-1037/dir-003/_0449.htm" target="main1">automatic dialing
automatic dialing: See automatic calling unit.
@@
href="/fs-1037/dir-004/_0450.htm" target="main1">Automatic Digital Network (AUTODIN)
Automatic Digital Network (AUTODIN): Formerly, a worldwide data communications network
of the Defense Communications System, now replaced by the Defense Switched Network (DSN).
(188)
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href="/fs-1037/dir-004/_0451.htm" target="main1">automatic error correction
automatic error correction: See error-correcting code.
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href="/fs-1037/dir-004/_0452.htm" target="main1">automatic exchange
automatic exchange: In a telephone system, an exchange in which communications among users
are effected by means of switches set in operation by the originating user equipment without
human intervention at the central office or branch exchange.
@@
href="/fs-1037/dir-004/_0453.htm" target="main1">automatic frequency control (AFC)
automatic frequency control (AFC): A device or circuit that maintains the frequency of an
oscillator within the specified limits with respect to a reference frequency.
@@
href="/fs-1037/dir-004/_0454.htm" target="main1">automatic function
automatic function: A machine function or series of machine functions controlled by a program
and carried out without assistance of an operator.
@@
href="/fs-1037/dir-004/_0455.htm" target="main1">automatic gain control (AGC)
automatic gain control (AGC): A process or means by which gain is automatically adjusted in a
specified manner as a function of a specified parameter, such as received signal level. (188)
@@
href="/fs-1037/dir-004/_0456.htm" target="main1">automatic identified outward dialing
(AIOD)
automatic identified outward dialing (AIOD): A service feature of some switching or terminal
devices that provides the user with an itemized statement of usage on directly dialed calls. Note:
AIOD is facilitated by automatic number identification (ANI) equipment to provide automatic
message accounting (AMA).
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href="/fs-1037/dir-004/_0457.htm" target="main1">automatic link establishment (ALE)
automatic link establishment (ALE): 1. In high-frequency (HF) radio, the capability of a station
to make contact, or initiate a circuit, between itself and another specified radio station, without
human intervention and usually under processor control. Note: ALE techniques include
automatic signaling, selective calling, and automatic handshaking. Other automatic techniques
that are related to ALE are channel scanning and selection, link quality analysis (LQA), polling,
sounding, message store-and-forward, address protection, and anti-spoofing. 2. In HF radio, a
link control system that includes automatic scanning, selective calling, sounding, and transmit
channel selection using link quality analysis data. Note: Optional ALE functions include polling
and the exchange of orderwire commands and messages. (188)
@@
href="/fs-1037/dir-004/_0458.htm" target="main1">automatic message accounting (AMA)
automatic message accounting (AMA): A service feature that automatically records data
regarding user-dialed calls. (188)
@@
href="/fs-1037/dir-004/_0459.htm" target="main1">automatic message exchange (AME)
automatic message exchange (AME): In an adaptive high-frequency (HF) radio network, an
automated process allowing the transfer of a message from message injection to addressee
reception, without human intervention. Note: Through the use of machine-addressable transport
guidance information, i.e., the message header, the message is automatically routed through an
on-line direct connection through single or multiple transmission media.
@@
href="/fs-1037/dir-004/_0460.htm" target="main1">automatic message processing system
(AMPS)
automatic message processing system (AMPS): Any organized assembly of resources and
methods used to collect, process, and distribute messages largely by automatic means. [JP1]
@@
href="/fs-1037/dir-004/_0461.htm" target="main1">automatic number identification (ANI)
automatic number identification (ANI): A service feature in which the directory number or
equipment number of a calling station is automatically obtained. Note: ANI is used in message
accounting.
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href="/fs-1037/dir-004/_0462.htm" target="main1">automatic operation
automatic operation: The functioning of systems, equipment, or processes in a desired manner at
the proper time under control of mechanical or electronic devices that operate without human
intervention.
@@
href="/fs-1037/dir-004/_0463.htm" target="main1">automatic redial
automatic redial: A service feature that allows the user to dial, by depressing a single key or a
few keys, the most recent telephone number dialed at that instrument. Note: Automatic redial is
often associated with the telephone instrument, but may be provided by a PBX, or by the central
office. Synonym last number redial. Contrast with automatic calling unit.
@@
href="/fs-1037/dir-004/_0464.htm" target="main1">automatic reload
automatic reload: See bootstrap (def.#3)