Atto (10-18). See metric system.

Application and Service Capabilities

Access Border Gateway Function.

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.

Analog-to-digital. See analog transmission.

Assisted Global Navigation Satellite System (A-GNSS)

Assisted Global Positioning System

See 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: 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… (Read More →)

1. Audio and Video;
2. Audio/Video

1. Authentication, Authorization and Accounting Services;
2. Authentication, Authorization, Audit/Accounting

Advanced Audio Coding

ATM Adaptation Layer

Application Aware Networks

A call in which the call originator disconnects or cancels the call after a connection has been made, but before the call is established.

Network replacement of a connect signal with an on-hook signal (network) prior to receiving a CI (customer installation) answer signal; abandonment is the only way to end an unanswered call attempt. [T1.405-1989]

An address that has fewer characters than the full address, usually for special communications and other services or for certain users.
Note: Examples of abbreviated addresses are (a) a four-digit telephone number for a user calling another user connected to the same switching exchange, and (b) message addresses that have only the addressee name and station code or number. [After… (Read More →)

Calling that enables a user to employ an address having fewer characters than the full address when initiating a call.
Note: Communications network users may be allowed to designate a given number of abbreviated address codes. The allocation of the abbreviated address codes to a destination or group of destinations may be changed as required, by means of a suitable… (Read More →)

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.

Augmented Backus-Naur Form

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.

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,… (Read More →)

In communications, computer, and data processing systems, an address that directly identifies a storage location without the use of an intermediate reference, e.g., a base address or a relative address. [After Weik '96]

1. The time interval or phase difference between transmission and reception of a signal.
2. The total time between the instant a bit enters the network and the instant a corresponding bit exists the network. [T1.503-1989] [T1.507-1996]

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… (Read More →)

See thermodynamic temperature.

The ratio of the luminous flux or absorbed radiant flux to the incident flux.

In the transmission of electrical, electromagnetic, or acoustic signals, the conversion of the transmitted energy into another form, usually thermal. [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.

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]

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.

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 ,f01 where K is the absorption coefficient, is the wavelength in vacuum, and n… (Read More →)

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.

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.

1. The wavelength or frequency at which a particular substance absorbs the most power (or, where the attenuation of the propagated signal is the greatest) whenever the substance is bombarded or irradiated with audio, electromagnetic, or light waves.
Note: Whenever a material is thus bombarded, there is reflection, transmission through the material, and absorption within the material. In the case… (Read More →)

Of a material propagation medium, absorptance per unit path length.

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.

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… (Read More →)

1. Broadly, the use of specialized software, such as an application programming interface (API), as a means of shielding software from device dependencies or the complexities of underlying software.
Note: For instance, hardware abstraction enables programs to focus on a task, such as communications, instead of on individual differences between communications devices.
2. In object-oriented programming, the process of reducing… (Read More →)

1. Alternating current,
2. Access Criteria.

Dolby Audio Coding 3

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.

In data transmission, the condition assumed by a primary or secondary station upon correct receipt of a frame for processing.

The condition that exists when a system or functional unit meets the specified performance and security requirements.

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:… (Read More →)

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. [After 2196]

See acceptance test.

The bound on performance that is allowed at service turnup or interexchange carrier (IC) acceptance of a circuit or connection, or when corrective action is taken to restore a parameter after an immediate action limit (IAL) failure. Performance as measured by a parameter is satisfactory if the value of the parameter is equal to or better than the limit. [T1.208-1989]

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. [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… (Read More →)

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.

Operating and testing of a communication system, subsystem, or component, to ensure that the specified performance characteristics have been met.

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.

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]

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.
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.
4. (AIS) [The] ability and means to communicate… (Read More →)

An arrangement to transport access traffic between an end office and an IC POT (interexchange carrier point of termination) and may be either direct routed, tandem routed, or a combination of direct and tandem routed. (In the case of direct routed only, the access arrangement and access connection are synonymous. ) [T
1. Rpt 11-1991]

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.

In a communications system, a signal sent in the backward direction to indicate that a call will not be completed because of a call-originator or a call-receiver facility requirement.
Note: An access barred signal may occur for many reasons, such as the failure of a closed user group validation check on an incoming calls-barred facility. [After Weik '96]

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.

A designated part of the information transfer capability having specified characteristics, provided at the user-network interface. [T1.667-1999]

1. A fee charged by a local exchange carrier for the use of its local exchange networks. [FCC]
2. 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.

1. The preliminary digits that a user must dial to be connected to a particular outgoing trunk group or line.
2. A uniform code assigned by the telephone company to an individual customer in the form 101xxxx and 950-xxxx. [NECA/FCC-5]

In ISDN technology, a connection (using either the B-Channel or a logical link on the D-Channel) established between the user equipment and a packet-mode handier function, over which packet-mode calls (incoming and outgoing) are established. [After T1.615-1992]

In ISDN applications, synonym contention.

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… (Read More →)

1. In security, a list of entities, together with their access rights, that are authorized to access a resource.
2. [A] mechanism implementing discretionary and/or mandatory access control between subjects and objects. [INFOSEC-99]
3. A list associated with an object specifying the access rights of subjects to that object [CESG].
4. A set of control attributes. It is a list,… (Read More →)

1. In security, a hardware, software, or firmware feature, operating procedure, or management procedure that (a) permits authorized access to a system, such as a communications, computer, and data processing system, (b) prevents unauthorized access to the system, and (c) is considered to have failed when unauthorized access is permitted or when authorized access is prevented. [From Weik '96]
2.… (Read More →)

A message that is a user request, a resource controller response, or a request/response between resource controllers.

1. A set of rules, part of a security policy, by which human users, or their representatives, are authenticated and by which access by these users to applications and other services and security objects is granted or denied [ECMATR46].
2. The set of rules that define the conditions under which an access may take place [10181-3].
3. A set of… (Read More →)

Deprecated term. See directional coupler.

A three-digit alpha code assigned to identify Incumbent Local Exchange Carriers (ILECs) and Competitive Local Exchange Carriers (CLECs) associated with CICs.

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.

In automatic direct outward telephone dialing, a digit, often a 1, or a 9, that (a) enables access to an outside facility, e.g., a PBX or local exchange, and (b) is prefixed to the specific number being dialed.
Note 1: Throughout the United States, an access digit, usually 1, must be prefixed to an area code before dialing the area… (Read More →)

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.

A set of processes in a network that provides for interaction between the user and a network. [T1.667-1999]

The Access Gateway provides an access interface between multiple types of line side services and devices and the packet network. Examples of these services and devices are Plain Old Telephone Service (POTS) telephones, Basic Rate Interface (BRI) sets, Coin telephones, as well as some Digital Subscriber Line (DSL) and private lines/special services on 2 and 4 wire DS0, DS1 interfaces,… (Read More →)

A group of one or more stations having identical rights to use the available resources on a PBX, network or host computer.

1. In security, the level of authority required from an entity to access a protected resource.
Note: An example of access level is the authority to access information at a particular security level. [2382-pt.8]
2. [The] hierarchical portion of the security level used to identify sensitivity of information-system (IS) data and the clearance or authorization of users. Access level, in… (Read More →)

1. A transmission path between end user terminal equipment and a switching center.
2. A channel between an end user's network interface and local end office. [T1.506-1989] Synonym [loosely] loop.
3. A communications facility extending from a customer's premises to a serving central office comprising a subscriber line and, if necessary, a trunk facility, e.g., a WATS access line, TWX… (Read More →)

1. In information systems (IS), a compilation of users, programs, or processes and the access levels and types to which each is authorized. [INFOSEC-99]
2. In COMSEC, a roster of persons authorized admittance to a controlled area. [INFOSEC-99]

See attendant access loop.

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.

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.

The steps required to obtain the use of a system or device.
Note: Examples of access paths are (a) the operations required of a database management system to obtain access to a database and (b) the sequence of steps required to reach a file. [From Weik '96]

In security, a segment of time, generally expressed in days or weeks, during which specified access rights prevail. [INFOSEC-99]

All of a subject's access rights with respect to some object. [2382-pt.8]

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.

1. A point where connections may be made for testing or using particular communications circuits.
2. In telephony, a junction point in outside plant consisting of a splice at a junction between a branch feeder cable and distribution cables.

1. In security, a profile that associates each user with a list of protected objects that the user may access.
2. [An itemization that] associates each user with a list of protected objects the user may access. [INFOSEC-99]

1. An organization that provides users with access to a computer network. [2385-35]
2. A party responsible for traffic originating and terminating in jurisdictional areas defined by regulatory agencies. [T1.246-1998]

1. A control message issued by an access originator for the purpose of initiating an access attempt.
2. A signal sent to a network for the purpose of initiating the establishment of a network connection. In this definition, a signal may take the form of a message. [T1.507-1996]

1. Permission for a subject to access a particular object for a specific type of operation.
Note: An example of an access right is the permission for a process to read a file but not write to it. [2382-pt.8]
2. Authorization of access. Notes: [a] Access rights may be more or less explicit, both in the granularity of definition of… (Read More →)

A geographic area established for the provisioning and administration of telecommunications service. An access service area encompasses one or more exchanges, which are grouped in access service areas to serve common social, economic, and other purposes. Contrast with LATA. [After T1.104-1988]

The ordering form used to request Access Services, both Special and Switched.

In communications, computer, and data processing systems, a program that (a) allows an operator to call up different parts of the program package and (b) usually allows functions to be selected from menus in the same way as other commands.
Note: An example of an access system is the program supplied with a common spreadsheet program that (a) allows the… (Read More →)

1. A telephone company or centralized equal access provider switching system that provides a concentration and distribution function for originating or terminating traffic between end offices and a customer-designated premises. [NECA/FCC-5]
2. An exchange carrier switching system that provides a traffic concentration and distribution function for inter-LATA traffic originating/terminating within a LATA. [T1.506-1989]

The convergence of the full range of access technologies encompassing mobility, normadicity, and roaming between networks.

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… (Read More →)

1. In computer security, a type of operation specified by an access right.
Note: Examples of access type are "read," "write," "execute," "append," "modify," "delete," and "create. " [2382-pt.8]
2. [The] privilege to perform action on an object. Read, yywrite, execute, append modify, delete, and create are examples of access types. [INFOSEC-99]

See medium access unit (MAU).

Synonym attachment unit interface.

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.

With reference to point code, the ability of a local MTP (message transfer part) to send a message to the MTP at the remote signaling point. [T1.11
0. 2-1999]

1. Typically corresponds 1-to-1 to Subscriber.
2. Typically corresponds 1-to-1 to IPTV Customer.

1. The property that ensures that the actions of an individual or an institution may be traced uniquely to that individual or institution. [After X9.57]
2. In information systems (IS), the process of tracing IS activities to a responsible source. [INFOSEC-99]
3. In COMSEC, the principle that an individual is entrusted to safeguard and control equipment, keying material, and information… (Read More →)

1. Recording of the exercise of access rights to types of information specified in the System Security policy.
Note: The term "security accounting" may be used to avoid ambiguity. See also: Audit Trail.
2. A mechanism that keeps accurate track of a user's profile, usage, and service charges.

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… (Read More →)

1. In computer security, the authorization and approval--granted by a designated authority to a data processing system, computer network, organization, or individual--to process sensitive information or data. [2382-pt.8]
2. Formal declaration by a designated approving authority that an information system (IS) is approved to operate in a particular security mode using a prescribed set of safeguards at an acceptable level… (Read More →)

Synonym designated approving authority.

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.
3. A storage battery.

The degree of conformity of a measured or calculated value to its actual or specified value.

Abbreviation for automatic call distributor.

A usually two-element lens that is corrected to bring two specified or distinct wavelengths to a common focal point.
Note 1: The term "achromatic" literally means "without color. " This is not strictly true, however. Early lenses consisted of only a single element, and therefore could bring only a single wavelength to a given focal point; i.e., they suffered from… (Read More →)

Synonym achromat.

Synonym achromat.

1. acknowledge character.
2. acknowledge.

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.
See also ACK.

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… (Read More →)

Synonym [loosely] sliding window.

Architecture for Control Networks

Access Carrier Name Abbreviation

See Interexchange Access Customer (IAC Code)

1. An interface device for coupling electrical signals by acoustical means--usually into and out of a telephone instrument.
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.

A device that introduces a delay in the propagation of an electrical signal by (a) employing a transducer to convert the signal into an acoustic wave, (b) propagating the acoustic wave through a medium such as a column of mercury or a carbon or ferrite rod, and (c) by means of another transducer, converting the acoustic wave back to an… (Read More →)

1. An undesired audible disturbance in the audio frequency range.
2. Any undesired acoustic wave or signal, or undesired component of a desired acoustic signal, whether or not audible to the human ear; e.g., interference accompanying a sonar echo.

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… (Read More →)

The branch of science and technology that is devoted to the production, transmission, control, processing, transformation, reception, and effects of sound, longitudinal waves, particularly as vibration, pressure, or elastic waves and shock phenomena in material media. [After Weik '96]

A variation of the refractive index of a material caused by interaction with acoustic energy in the form of a wave or pulse.
Note: The acousto-optic effect is used in devices that modulate or deflect light.

The discipline devoted to the interactions between acoustic waves and light waves in a material medium. [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.

1. In satellite communications, the process of locking tracking equipment on a signal from a communications satellite.
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.

See ATOW.

1. In a communications system, the time interval required to attain synchronism.
2. In satellite control communications, the time interval required for locking trackingequipment on a signal from a communications satellite.

1. Alternate Carrier Routing.
2. Automatic Carrier Routing

Automatic Configuration Server

The operations and operands that form part of an attempted access [10181-3].

A Central Office code assigned by the CO Code Administrator and implemented in the PSTN for specific routing and rating requirements as of the LERG Routing Guide effective date.

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.

Used to differentiate package levels (e.g., item versus pallet).

A condition of readiness for a key to be used to secure information from the originator, and to process received secure information. [After X9.17]

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.

1. A satellite carrying a station intended to transmit or retransmit radio communication signals. [NTIA] [RR]
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.
2. An Earth satellite carrying a station intended to transmit or re-transmit radiocommunication signals. [47CFR]

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… (Read More →)

A signaling link that has successfully completed the initial alignment procedures and carries (or is ready to carry) signaling traffic. [T1.226-1992]

See star coupler, multiport repeater.

1. Any threat of a deliberate unauthorized change to the state of a data processing system.
Note: For example, an active threat that would result in modification of messages, insertion of spurious messages, masquerade, or denial of service [2382-pt.8].
2. The threat of a deliberate unauthorized change to the state of the system.
Note: Examples of security-relevant active threats may… (Read More →)

The process of comparing each output video frame with its preceding frame(s) in sequence and quantifying the extent of correspondence between each pair; when there is limited correspondence between a pair of frames (such that the differences measured are distinguishable from the measurement noise), and the corresponding input sequence of frames possesses distinguishable differences, then the current frame is categorized… (Read More →)

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.

Automatic calling unit

Administrative Domain

Synonym click-through.

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.

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.
Note: The modification of a system parameter may be discrete, as in hard-switched diversity reception, or may… (Read More →)

In computer science, a software-oriented compression process based on continuous analysis of the data stream, and depending on the type and content of the data and the storage medium, corresponding compensation of the compression algorithm.

Differential pulse-code modulation in which the prediction algorithm is adjusted in accordance with specific characteristics of the input signal.

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.

In ADPCM coding, a time-varying process that computes an estimate of the input signal from the quantized difference signal. [T1.310-1991]

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… (Read More →)

In ADPCM (adaptive differential pulse code modulation) coding, a process in which the quantizer step size varies as a function of the quantized input signal's variance. [T1.310-1991]

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.

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.

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.

The official, high-level computer language of DOD for embedded-computer, real-time applications as defined in MIL-STD-181
5.
Note: Ada® is a registered trademark of the U. S. Government (Ada Joint Program Office).

1. Analog-to-digital converter,
2. analog-to-digital conversion.

Advanced Data Communication Control Procedures

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.

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.

A multiplexing function offered in connection with SONET that allows lower level signals to be added or dropped from a high-speed optical carrier channel in a wire center. The connection to the add/drop multiplexer is via a channel to a central office port at a specific digital speed (i.e., DS3, DS1, etc. ). [NECA/FCC-5]

A bit delivered to the intended destination user in addition to intended user information bits and delivered overhead bits. Synonym extra bit.

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.

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… (Read More →)

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.

White noise

1. In communications, the coded representation of the source or destination of a message.
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.
3. To assign to a device or item of data a label to identify its location.
4. The part of… (Read More →)

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.

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.

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.

A part of an instruction that usually contains only an address or part of an address.

A prescribed structure of data used to represent the destination(s) of a block, message, packet, or other formalized data structure.

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.

A character that separates the different addresses in a selection signal.

A process used to convey address information; two address signaling methods, dial pulse (DP) and dual tone multifrequency (DTMF), are used in telephone systems. [After T1.401-1988]

The mapping from one value or format to another value or format that identifies the equivalent end-target destination. An ENUM example is the mapping of an E.164 DN to a SIP URI address, both of which identify the called party.

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.

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… (Read More →)

In computer graphics, any point of a device that can be addressed.

Abbreviation for automatic data handling.

A circuit that avoids loss or gain of heat. For example, a computer could clear a "1" in a register by subtracting the "1" instead of erasing it, thereby expending less heat.

Two signaling points that are directly interconnected by one or more signaling links. [T1.226-1992]

Extraneous power from a signal in an adjacent channel.
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.

An intelligent-network feature that resides at the intelligent peripheral equipment and responds to service logic interpreter requests for service processing.

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… (Read More →)

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. [After T1.218-1991]

Administrative numbers are numbers used by telecommunications carriers to perform internal administrative or operational functions necessary to maintain reasonable quality of service standards. Examples of administrative numbers are: Test numbers, employee/official numbers, Location Routing Numbers, Temporary Local Directory Numbers, soft dial tone numbers and Pseudo Automatic Number Identification (pANI) numbers (47 CFR §5
2. 15 (f)(1) (i) and FCC 00-104… (Read More →)

A four character numeric or alphanumeric that identifies the administrator of one (1) or more data records contained in the iconectiv® BIRRDS. If a Service Provider (SP) performs its own record administration, the Operating Company Number (OCN) value is most often the same value as an OCN Assigned to that company based on a National Exchange Carrier Association (NECA) Assigned… (Read More →)

Abbreviation for automatic data processing.

Synonym computer system.

Abbreviation for adaptive differential pulse-code modulation.

Abbreviation for automatic data processing equipment.

Asymmetric Digital Subscriber Line

Asymmetric Digital Subscriber Line 2+

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).

1. A telecommunications network architecture that uses databases to facilitate call processing, call routing, and network management, allowing carriers to change the routing of both inbound and outbound calls from moment to moment. [FCC-5]
2. A proposed intelligent-network (IN) architecture that includes both IN/1+ and IN/2 concepts.

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).

Abbreviation for Aeronautical Emergency Communications System. See Aeronautical Emergency Communications System Plan.

A communications cable designed for installation on, or suspension from, a pole or other overhead structure.

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,… (Read More →)

An aeronautical station used for advisory and civil defense communications primarily with private aircraft stations. Synonym UNICOM station. [NTIA]

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]

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]

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]

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]

A station in the aeronautical fixed service. [NTIA][RR]

An aeronautical mobile service intended for communications, including those relating to flight coordination, primarily outside national or international civil air routes. [NTIA] [RR]

An aeronautical mobile service reserved for communications relating to safety and regularity of flight, primarily along national or international civil air routes. [NTIA] [RR]

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]

An aeronautical mobile-satellite service intended for communications, including those relating to flight coordination, primarily outside national and international civil air routes. [NTIA] [RR]

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]

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]

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]

A radionavigation service intended for the benefit and for the safe operation of aircraft. [NTIA] [RR]

A radionavigation-satellite service in which Earth stations are located on board aircraft. [NTIA] [RR]

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]

Advanced Encryption Standard

Abbreviation for: 1) Audio Frequency, 2) Assured Forwarding, 3) Application Functions

Active Format Description

Acronym for Association Francaise de Normalisation. France's national standards-setting organization.

Abbreviation for automatic gain control.

Synonym droid.

In security, the acquisition of sensitive information by collecting and correlating information of lesser sensitivity. [2382-pt.8]

Any entity that, in the ordinary course of its operations, makes telephones available to the public or to transient users of its premises, for interstate telephone calls using a provider of operator services. [NECA/FCC-5]

Aging numbers are disconnected numbers that are not available for assignment to another end user or customer for a specified period of time. Numbers previously assigned to residential customers may be aged for no more than 90 calendar days. Numbers previously assigned to business customers may be aged for no more than 365 calendar days (FCC 00-104 §5
2. 15… (Read More →)

A term used to refer to the complete set of inter-entity arrangements that are necessary for communications services; these arrangements include national and international standards; federal, state and local regulations or other legal arrangements; or any other agreement between entities - including industry cooperation and agreements and other interfaces between entities. ASPR is one of the elements of the Eight… (Read More →)

Abbreviation for Access Gate Way.

Abbreviation for artificial intelligence or Airborne Internet

Abbreviation for amplitude intensity modulation. See intensity modulation.

Abbreviation for advanced intelligent network.

Abbreviation for automatic identified outward dialing.

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. . . . [47CFR]

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]

Measuring atmospheric phenomena or determining atmospheric conditions, especially by means of apparatus carried by balloons, rockets, or satellites.

In grounding systems, the lightning rod or conductor placed on or above a building, structure, or external conductors for the purpose of intercepting lightning.

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.

Synonym floating head.

A radio service in which common carriers are authorized to offer and provide radio telecommunications service for hire to subscribers in aircraft. [47CFR]

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.

A coaxial cable in which air is the primary dielectric (insulator) between the inner and outer conductors.
Note: Proper separation between the inner and outer conductors is maintained by a continuous helical insulator or a series of insulating washers spaced at regular intervals.

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.

A mobile Earth station in the aeronautical mobile-satellite service located on board an aircraft. [NTIA] [RR]

An international aeronautical emergency frequency, such as
12
1. 5 MHz (civil) and
24
3. 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.

A mobile station in the aeronautical mobile service, other than a survival craft station, located on board an aircraft. [RR]

An aeronautical station providing communication between an airdrome control tower and aircraft. [NTIA] Synonym airport control station.

Synonym airdrome control station.

Abbreviation for: 1)alarm indication signals, 2) automated information system.

Asynchronous Java and XML

Authentication and Key Agreement

An alerting indication to a condition that may have immediate or potential negative impact on the state of the monitored network element (NE). [T1.226-1992]

A location that receives local and remote alarms.
Note: An alarm center is usually in a technical control facility.

An instantaneous occurrence that changes at least one of the attributes of the alarm status of an object. This status change may be persistent or temporary, thus allowing for surveillance, monitoring, and performance measurement functionality, etc. Alarm events may or may not generate alarm reports; they may trigger other events or may be triggered by one or more other events.… (Read More →)

1. A signal transmitted in lieu of the normal signal to maintain transmission continuity and to indicate to the receiving equipment that there is a transmission interruption located either at the equipment originating the AIS signal or upstream of that equipment. [T1.231-1997]
2. A signal transmitted in lieu of the normal signal to maintain transmission continuity and indicate to the… (Read More →)

A device that responds to a signal from an alarm sensor.
Note: Examples of alarm indicators include bells, lamps, horns, gongs, and buzzers.

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.
2. In a… (Read More →)

A set of attributes that describes the alarms currently defined for an object, for example, perceived severity, alarm state, etc. The alarm status of an object is a subset of the global status of that object. [T1.215-1990]

A set of functions that enables the monitoring or interrogation (or both) of the telecommunications network concerning alarm-related events or conditions. [T1.215-1994]

Asynchronous Layered Coding

Abbreviation for automatic link establishment.

A textual or numeric label unique to each alert event which may be used by receiving devices to identify a given alert message as a duplicate transmission of a previously-processed alert. This identifier may be provided by the Service Provider to consumer-domain devices to allow the ITF to avoid re-displaying previously displayed alert messages.

An integer value that indicates the priority of the alert

A signal used by the network to indicate the presence of an incoming call. It consists of a ringing signal periodically interrupted by silent (no ringing signal) intervals. [T1.401-1988]

Application Layer Gateways

In encryption, a unique identifier or recognizer for a given encryption or hash algorithm, together with any required parameters. [After X9.31-1]

An artificial language established for expressing a given class of algorithms.

Automatic Location Identification

1. See aliasing.
2. In networking, one of a set of domain names of an Internet resource. [2382-pt.35]
3. Synonyms personal number, UPT number.

1. A Signaling System No.7 (SS7) address that is shared by more than one system supporting the same GTT (global title translation) function (or other SS7 function). It allows other systems to address the function instead of maintaining the status of multiple point codes. [T1.711-1999]
2. A point code that may be assigned to more than one signaling point, each… (Read More →)

In any technology or process involving (a) sampling a signal, e.g., an electrical signal or (a series of images of) a moving subject; (b) processing, storing, or transmitting representations of the samples; and (c) replicating the original signal from the representations: the production of artifacts as a result of sampling at intervals too great to permit faithful replication of the… (Read More →)

A bundle of optical fibers in which the relative spatial coordinates of each fiber are the same at the two ends of the bundle.
Note: Such a bundle may be used for the transmission of images. Synonym coherent bundle.

A procedure by which the error rate of a signaling link is measured during the initial alignment process. [After T1.11
0. 2-1992] [After T1.226-1992]

The short-term variations between the optimum sampling instants of a digital signal and the sampling clock derived from it. [T
1. Rpt17-1993]

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.

Synonym 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.

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.

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]

ATIS: Alliance for Telecommunication Industry Solutions. ATIS is committed to providing leadership for, and the rapid development and promotion of, worldwide technical and operations standards for information, entertainment and communications technologies using a pragmatic, flexible, and open approach.

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… (Read More →)

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]

Aggregated Line and Node Protection

See power-law index profile.

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… (Read More →)

Deprecated synonym for alphabet transliteration. See 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.
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… (Read More →)

A character set that contains letters and may contain control characters, special characters, and the yyspace character, but not digits.

A code according to which data are represented through the use of an alphabetic character set.

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.

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.

1. Pertaining to a character set that contains letters, digits, and sometimes other characters, such as punctuation marks.
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.

A character set that contains both letters and digits, special characters, and the yyspace character.

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.

Data represented by letters, digits, and sometimes by special characters and the yyspace character.

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.

In encryption, the process of changing one or more message elements in a message as a means of committing a fraud. [After X9.19]

A company that enters a market area as a competitive service provider (CAP) to provide exchange service in competition with one or more existing exchange carrier(s) in the same market area. [After T1.251-1996]

A special advanced intelligent network (AIN) feature supporting Government Emergency Telecommunications Service (GETS) calls. The feature automatically routes GETS calls to selected carriers to provide improved call completion probability during times of network congestion or damage during disasters or crises.

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. Synonym bipolar signal.

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… (Read More →)

A second or subsequent choice path between two points. [T
1. Rpt24-1993]

1. The routing of a call or message over a substitute route when a primary route is unavailable for immediate use.
2. In signaling, the process of allocating substitute routes for a given signaling traffic stream in case of failure(s) affecting the signaling links or routes involved in the normal routing of that signaling traffic stream. [T1.226-1992]
3. In signaling,… (Read More →)

Synonym half-duplex (HDX) operation.

1. In signaling, the process of allocating substitute routes for a given signaling traffic stream in case of failure(s) affecting the signaling links or routes involved in the normal routing of that signaling traffic stream. [T1.226-1992]
2. In signaling, the routing of a given signaling traffic flow in case of failures affecting the signaling link(s), or route(s), involved in the… (Read More →)

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… (Read More →)

Abbreviation for arithmetic and logic unit.

Abbreviation for amplitude modulation.

Access Management Functional Entity

Amplitude Modulated - Vestigial Sideband

Abbreviation for automatic message accounting.

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]

A station in the amateur service. [NTIA] [RR]

A radiocommunication service using space stations on Earth satellites for the same purposes as those of the amateur service. [NTIA] [RR]

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)… (Read More →)

The temperature of air or other media in a designated area, particularly the area surrounding equipment.

Abbreviation for amplitude modulation equivalent, automatic message exchange. See compatible sideband transmission.

The U. S. standards organization that establishes procedures for the development and coordination of voluntary American National Standards.

See ASCII.

Abbreviation for alternate mark inversion. See alternate mark inversion signal.

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.

1. An electronic component that boosts the voltage or power level of a signal that is a linear replica of the input signal, but with greater power or voltage level, and sometimes with an impedance transformation. The output may also be a nonlinear analog function of the input signal, as in a signal compression device.
2. See fiber amplifier, optical… (Read More →)

1. See signal compression.
2. In video production, the imposition of a nonlinear transfer function on (i.e., the nonlinear processing of, to reduce the dynamic range of) signal amplitude values (e.g., as in gamma correction). [After SMPTE]

Distortion occurring in a system, subsystem, or device when the output amplitude is not a linear function of the input amplitude under specified conditions.
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.

A corrective network that is designed to modify the amplitude characteristics of a circuit or system over a desired frequency range.
Note: Such devices may be fixed, manually adjustable, or automatic.

See hit.

Deprecated term. See intensity modulation.

Keying in which the amplitude of a signal is varied among the members of a set of discrete values.

Modulation in which the amplitude of a carrier wave is varied in accordance with some characteristic of the modulating signal.
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… (Read More →)

Synonym compatible sideband transmission.

Distortion in a transmission system caused by nonuniform attenuation, or gain, in the system with respect to frequency under specified operating conditions. Synonym frequency distortion.

1. automatic message processing system.
2. Advanced Mobile Phone System.

Abbreviation for automated maritime telecommunications system.

Access Node

Synonym CAV.

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… (Read More →)

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.

The portion of the digital-to-analog conversion process that generates an analog signal value from the digital signal that resulted from analog encoding.
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.

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.
Note: Multiple samples are needed to digitize a waveform over a time interval.

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.

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.
2. A nominally continuous electrical signal that varies in some direct correlation with another signal impressed on a transducer.
Note: For example, an analog signal may… (Read More →)

The data link that provides an interface to signaling terminals and is made up of voice-frequency analog transmission channels and modems. [T1.11
0. 2-1992]

Switching equipment designed, designated, or used to connect circuits between users for real-time transmission of analog signals.

Transmission of a continuously varying signal as opposed to transmission of a discretely varying signal.

Synonym analog-to-digital converter (ADC).

Synonym analog-to-digital converter (ADC).

A device that converts an analog signal to a digital signal that represents equivalent information. Synonyms analog-to-digital (A-D) coder, analog-to-digital (A-D) encoder.

An attempt to break a code or to find a key using analytical methods.
Note: Examples of an analytical attack are: a statistical analysis of patterns; a search for flaws in an encryption algorithm. [2382-pt.8] Synonym cryptanalytical attack.

Modulation in which the phase or frequency of a sinusoidal carrier is varied.
Note: Phase and frequency modulation are particular forms of angle modulation.

In optics, the net angular deflection experienced by a light ray after one or more refractions or reflections.

The angle between an incident ray and the normal to a reflecting or refracting surface.

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.

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.

1. automatic number identification.
2. application-to-network interface.

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.

See asynchronous transmission.

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… (Read More →)

Abnormal propagation caused by fluctuations in the properties (such as density and refractive index) of the propagation medium.
Note: AP may result in the reception of signals well beyond the distances usually expected.

A 7- or 10-digit call to the directory number of the public service answering point (PSAP) (where applicable) causing the E911 system (emergency 9-1-1 system) to send to the PSAP a multifrequency (MF) pulse train devoid of the caller's emergency service identification. [T1.414-1998]

The name of a file-transfer protocol that allows a user on one host to access and transfer files to and from another host over a network. [After 2382-pt.35]

Abbreviation for American National Standard.

Abbreviation for American National Standards Institute.

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.… (Read More →)

A signal sent by receiving equipment to the sending station to indicate that the receiver is ready to accept transmission.

A signal indicating acceptance of the call by the addressed user. [T1.507-1996]

1. 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.
2. An off-hook signal transmitted towards the network when the called party answers.
3.… (Read More →)

The term "Answer/Disconnect Supervision" denotes the transmission of the switch trunk equipment supervisory signal (off-hook or on-hook) to the customer's point of termination, typically as an indication that the called or calling party has answered or disconnected.

1. Any structure or device used to collect or radiate electromagnetic waves.
2. A device that converts radio frequency electrical energy to radiated electromagnetic energy and vice versa; in a transmitting station, the device from which radio waves are emitted. [47CFR]

See aperture.

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.

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… (Read More →)

A device used to match the impedance of a transmitter and/or receiver to an antenna to provide maximum power transfer.

A power loss resulting from changes in the measurable impedance of a practical antenna from a value theoretically calculated for a perfect antenna.

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… (Read More →)

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.

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]

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… (Read More →)

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.

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.
Note: In general, a different antenna height above average terrain will be determined in each direction from the antenna. The average of these eight… (Read More →)

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.

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.
Note: The impedance of either the transmission line, or the antenna, or both, may be adjusted to effect the match.

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.
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… (Read More →)

Synonym left-hand polarized wave.

Pertaining to equipment, processes, or techniques used to reduce the effect of natural and man-made noise on radio communications.

Measures ensuring that intended transmitted information can be received despite deliberate jamming attempts. [INFOSEC-99]

A point in a standing wave at which the amplitude is a maximum.

1. Measures taken to prevent an unauthorized person/entity from impersonating an authorized person/entity to gain access to a data system. [DoJ]
2. Measures preventing an opponent's participation in an information system (IS). [INFOSEC-99]

A computer program designed to detect computer-file viruses and possibly to suggest or take corrective action. Synonym vaccine program. [After 2382-pt.8]

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… (Read More →)

ASM uses only the group address to identify the session traffic, noted as (*,G). The group address used must be unique within the network since ASM does not differentiate between (S1,G) and (S2,G) as unique multicast groups.

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.

Address of Record

Abbreviation for: 1)anomalous propagation, 2) application points, 3) access point.

Abbreviation for adaptive predictive coding.

Abbreviation for avalanche photodiode.
Note: apdand a. p. d. are also used.

Application Protocol Data Unit

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.

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.
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]

1. In a scanned image system, electrical compensation for the distortion introduced by the limiting size of a scanning aperture. [IEEE 100; After SMPTE]
2. In television technology, restoration of the depth of modulation to the higher (i.e., higher Fourier) frequency components of the video signal, with the objective of achieving a subjective improvement in image quality. [After SMPTE]
Note:… (Read More →)

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.

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.

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… (Read More →)

Applications Programming Interface

Alternative Positioning, Navigation, and Timing

ATIS Point of Deployment (a. k. a. , VueKey)

In an orbit of a satellite orbiting the Earth, the point that is farthest from the gravitational center of the Earth.

See altitude of the apogee or of the perigee.

Abbreviation forapplication, application software.

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… (Read More →)

A small, self-contained computer program that usually performs a task as part of, or under the control of, a larger software application. For example, most modern World Wide Web browsers are capable of making use of applets written in the Java programming language to perform simple tasks such as display animations or more complex tasks such as spreadsheet and database… (Read More →)

1. Software that embodies the primary logic characterizing and supporting an end-user service and its features. Such an application may reside on an application server (AS) within a service provider's network or may be a 3rd Party application outside of a service provider network.
2. Software on user devices providing something of value consumed by the end user. e.g., Microsoft… (Read More →)

A cooperative relationship between two application entities, formed by their exchange of application protocol control information through their use of presentation services. [T1.215-1990]

The system-independent application activities that are made available as application services to the application agent, e.g., a set of application service elements that together perform all or part of the communication aspects of an application process. [T1.667-1999]

See Open Systems Interconnection--Reference Model.

Synonym platform.

See application.

1. A formalized set of software calls and routines that can be referenced by an application program in order to access supporting network services.
2. The interface between the application software and the application platform, across which all services are provided. The application program interface is primarily in support of application portability, but system and application interoperability are also supported… (Read More →)

A set of rules and formats (semantic and syntactic) that determines the communication behavior of application entities in the performance of application functions. [T1.208-1989]

1. An application server is a physical computer or software only that supports a runtime environment for applications. The system software is an intrinsic part of the application server. Application servers ease application development by providing a suite of system software building blocks.
2. A physical computer that supports a runtime environment for applications. The system software is an intrinsic… (Read More →)

A coherent set of integrated functions to help accomplish application communication, e.g., within an application entity. [T1.667-1999]

1. Synonym application.
2. Software that is specific to an application and is composed of programs, data and documentation [POSIX.0].

Circuit components added to an existing system to provide additional or alternate functions.
Note: Applique may be used to modify carrier telephone equipment designed for ringdown manual operation to allow for use between points having dial equipment.

A small (pocket-size or smaller), specialized, portable computing device, with a self-contained power source, designed to (a) accept as inputs; (b) store; and (c) read out, user-designated information, usually appointments, telephone numbers, etc.

Deprecated synonym for protected distribution system.

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]

See computer architecture, network architecture.

A software file that has been set aside, often in a redundant storage medium, as a security measure or for later retrieval, e.g., for research or verification.

The storing of files, records, and other data for reference and alternative backup.

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… (Read More →)

See access code, code, country code, N code.

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… (Read More →)

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 .

Association of Radio Industries and Businesses

A part of a computer that performs arithmetic, logic, and related operations.

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.
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… (Read More →)

A register that holds the operands or the results of operations such as arithmetic operations, logic operations, and shifts.

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… (Read More →)

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.

In a processor, the part that performs arithmetic operations; sometimes the unit performs both arithmetic and logic operations.

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.

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… (Read More →)

Abbreviation for address resolution protocol.

Abbreviation for Advanced Research Projects Agency Network. A packet-switching network used by the Department of Defense, later evolved into the Internet.

Active Reader Passive Tag

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. Synonyms error-detecting-and-feedback system, repeat-request… (Read More →)

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.

A processor capable of executing instructions in which the operands may be arrays rather than data elements. Synonym vector processor.

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. Synonymssurge protective device, surge suppressor.

Abbreviation for automatic route selection.

Synonym [loosely] artificial transmission line.

Synonym posting.

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.
Note: The articulation index is affected by noise, interference, and distortion.

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.

In facsimile or television, a defect or distortion of the image, introduced along the sequence from origination and image capture to final display.
Note 1: Artifacts may arise from the overload of channel capacity by excess signal bandwidth.
Note 2: In general, artifacts may result from (a) sampling effects in temporal, spatial, or frequency domains, (b) processing by the transfer… (Read More →)

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,… (Read More →)

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. Synonym [loosely] art line.

Abbreviation for audio response unit.

1. Abbreviation for:
1. application server;
2. autonomous system.

Agile Service Assembly Process

Agile Service Creation

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.
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… (Read More →)

Authorized Service Domain

1. Application Services Interface;
2. Asynchronous Serial Interface

Any-Source Multicast

Abstract Syntax Notation

Access Service Ordering Guidelines

Automatically Switched Optical Network

1. adjunct service point;
2. application service provider.

1. In facsimile or television, the ratio of the width to the height of a scanning field or image.
Note: For example, the classical NTSC television standard specifies an aspect ratio of 4:3, and the new high-definition television standard specifies 16:
9.
2. The ratio of the width to the height of any video or scanned image display.

Automated Storage and Retrieval System

To translate a computer program expressed in an assembly language into a machine language.

A computer program that is used to assemble. Synonym assembly program.

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]

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. Synonym computer-dependent language.

Synonym assembler.

The elapsed time taken for the execution of an assembler.

1. In security, a resource or information that is to be protected. [After CC-99]
2. Any system or component (e.g., subsystem, hardware, firmware, software, database, or interconnection communications network or facility) that is part of a communications system or an information system. [After FAA]

1. The center of the assigned frequency band assigned to a station. [RR]
2. The frequency of the center of the radiated bandwidth.
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… (Read More →)

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]

Assigned numbers are numbers working in the PSTN under an agreement such as a contract or tariff at the request of specific end users or customers for their use, or numbers not yet working but having a customer service order pending. Numbers that are not yet working and have a service order pending for more than five calendar days shall… (Read More →)

For NS/EP, the designation of priority level(s).

Authorization given by an administration for a radio station to use a radio frequency or radio frequency channel under specified conditions. [NTIA] [RR]

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.
Note: In associated common-channel signaling, the signaling is usually accomplished by using the same facilities as the associated trunk group.

An Associated Location is a location (civic, geodetic or polygon) within the designated PSAP jurisdiction that may be used in wireless call scenarios to route a call toward the designated PSAP. The Associated Location is determined via a static mapping from the cell/sector ID received in incoming signaling to a routing location which, when used to query the routing database,… (Read More →)

A functional element in a NENA i3 system that uses the LoST protocol [RFC 5222] where location information (either civic address or geo-coordinates) and a Service URN serve as input to a mapping function that returns a URI used to route an emergency call toward the appropriate PSAP or responding agency based on the caller’s location.

The mode in which messages for a signaling relation involving two adjacent signaling points are conveyed over a directly interconnecting signaling link. [T1.226-1992]

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.

1. Grounds for confidence that an information-technology (IT) product or system meets its security objectives.
2. In INFOSEC, see information assurance.
3. A more general term than "confidence" indicating the particular measures that can be taken to establish confidence [CESG].
4. The confidence that may be held in the security provided by a Target of Evaluation[ITSEC].

A data compression technique that requires more processing capability to compress than to decompress.
Note: Asymmetric compression is typically used for the mass distribution of programs on media such as CD ROM, where significant expense can be incurred for the production and compression of data but the retrieval (or the playback) system must be low in cost. [After Silicon]

A cryptographic formula that uses two related keys—a public key and a private key—each of which has the characteristic algorithm that, given the public key, it is computationally infeasible to derive the private key. [After X9.62]

1. An access technology that allows voice and high-speed data to be sent simultaneously over local exchange service copper facilities; the technology supports data rates of up to
1. 544 Mb/s when receiving data (downstream rate) and up to 256 kb/s when sending data (upstream rate).
2. A modem technology that provides enhanced and affordable access to the Internet, live… (Read More →)

An encryption system that utilizes two keys, one called a public key (which is known to both the sender and the recipient of encrypted data), and the other, called a private key (known only to the individual sending the data).
Note: Data are encrypted with the private key and decrypted with the public key. Asymmetric encryption allows for the secure… (Read More →)

Synonym unbalanced modulator.

A data communications system that uses asynchronous operation.
Note: The time spacing between successive data characters or blocks may be of arbitrary duration. Synonym start-stop system. [T
1. X1]

A multiplexed transmission system in which the rates of the carrier and its tributaries are not traceable to the same master clocking source.
Note: In this type of system, extra signal elements are usually appended to the individual tributary signals for the purpose of interleaving them at a rate consistent with the carrier rate. [T
1. X1]

A network in which the clocks do not need to be synchronous or mesochronous. Synonym nonsynchronous network.

1. A sequence of operations in which operations are executed out of time coincidence with any event.
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. Synonym asynchronous working.

Time-division multiplexing in which asynchronous transmission is used.

A high-speed multiplexing and switching method utilizing fixed-length cells of 53 octets 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.

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.

Synonym asynchronous operation.

A de facto standard for modem commands from an attached CPU, used in most 1,200 and 2,400 b/s modems.

Analog Terminal Adapter

Abbreviation for all trunks busy.

Abbreviation for asynchronous time-division multiplexing.

A (terminating) IMS-based NG9-1-1 Service Architecture provides transit, routing, and other services required to support citizen-to-authority multimedia emergency services between the originating network and the emergency authority, e.g., PSAP. The IMS-based NG9-1-1 Service Architecture includes the i3 Legacy Network Gateway and i3 Legacy PSAP Gateway.

Abbreviation for asynchronous transfer mode.

A virtual channel connection (VCC) or a virtual path connection (VPC). [T1.627-1993]

An association established by the ATM Layer to support communication between two or more ATM service users (i.e., two or more next higher layer entities or two or more ATM Management entities). The communication over an ATM Layer connection may be either bidirectional or unidirectional. When bidirectional, two virtual channel connections (VCCS) are used. When unidirectional, only one VCC is… (Read More →)

A transport system composed of a carrier system terminated by an ATM multiplexer at each end. The relationship between input and output, i.e., virtual circuits, cannot change on a per call basis, i.e., permanent virtual circuits only are supported. This device does not allow blocking or signal compression. [T
1. Rpt46-1996]

A virtual path link (VPL) or a virtual channel link (VCL). [T1.627-1993]

1. With reference to both analog and digital interfaces, the ATM functional unit and technology that operates with analog 2-wire interfaces and standard digital line rates on both the inputs and the outputs, e.g., DS1 on the input and DS3 on the output, and which passes the cells received on the input to the output. The relationship between input and… (Read More →)

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.
Note: The reduced refractive index at the… (Read More →)

Radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorms.

See International Atomic Time.

Acronym for acquisition and tracking orderwire. A downlink circuit that provides a terminal with information regarding uplink acquisition and synchronization status.

Advanced Television Systems Committee

In e-mail, a computer file that is transmitted with an e-mail message.
Note: Attachments are converted by an e-mail manager program, or by an add-on, to a MIME (multipurpose Internet mail extension) or binary format. The files are recovered by the recipient's e-mail manager program or by an add-on into their original, usually application-specific, format. [Bahorsky]

In a local area network, the interface between the medium access unit (MAU) and the data terminal equipment within a data station.

1. An attempt to violate computer security.
Note: An example of an attack is malicious logic. [2382-pt.8]
2. [An] intentional act of attempting to bypass one or more of the following security controls of an information system (IS): nonrepudiation, authentication, integrity, availability, or confidentiality. [INFOSEC-99]

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,… (Read More →)

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. Synonym access loop.

A network-provided service feature that allows an attendant to establish a conference connection of three or more users.

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.

In [a] trusted-computing-base (TCB) design, a character entered from a terminal that tells the TCB the user wants a secure communications path from the terminal to some trusted node to provide a secure service for the user. [INFOSEC-99]

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]

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… (Read More →)

The rate of diminution of average power with respect to distance along a transmission path.
Note: The attenuation coefficient is often calculated as the sum of the absorption coefficient and the scattering coefficient. Synonym attenuation rate.

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.

The difference in loss at specified frequencies relative to the loss at 1004 Hz, unless otherwise specified. [NECA/FCC-5]

Synonym attenuation coefficient.

The condition that prevails when attenuation, rather than bandwidth, limits the performance of a communications link.

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… (Read More →)

1. In database management, a property inherent in an entity or associated with that entity for database purposes.
2. In network management, a property of a managed object that has a value.
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.

1. In computer security, an entity that is trusted by at least two entities to create and assign attribute certificates. [After X9.45]
2. An authority recognized in a security domain as a trusted source of attributes for entities within the domain. (See also Subject Authority) [ECMA138].

A set of attributes and a public key certificate identifier that are made unforgeable by use of the digital signature created with a private key. [After X9.30]

ADSL Transmission Unit, Central Office

ADSL Transmission Unit, Intermediate

ADSL Transmission Unit, Remote

Abbreviation for advanced television.

Authentication Center

Synonym for audible ringing tone.

An audible signal (information tone) transmitted to the calling party when the called party is alerted. [T1.401-1988]

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.
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… (Read More →)

A means for delivering audio signals from one point to another. An audio waveform submitted to the channel input results in a similar (not necessarily identical) waveform at the channel output. The audio channel may be comprised of the following components: encoders (compressors) and decoders (decompressors), buffers, multiplexors and demultiplexors, modulators and demodulators, transmission facilities, switches, multipoint conference units, and… (Read More →)

1. In videotape editing, a process or technique employed to (a) enhance (e.g., remove noise from, or introduce some kind of special effect into), (b) add to, or (c) replace totally, the originally recorded audio (if any), without modifying the originally recorded video signal.
2. In audiotape editing or mixing, a process analogous to any of the above, performed (a)… (Read More →)

A presentation unit of the audio channel; a group of consecutive audio samples. The preferred number of samples in an audio frame depends on the audio sample rate. These audio frames have no relationship to the frames designated by certain audio/speech codecs. [T1.80
1. 04-1997]

The band of frequencies (approximately 20 Hz to 20 kHz) that, when transmitted as acoustic waves, can be heard by the normal human ear.

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… (Read More →)

A video recording, mixing or switching technique or process in which the audio signal associated with any given video signal is recorded, switched, or mixed with that video signal.

An EAS alert message that when processed by the Endec and the EIS and displayed by the ITF contains both audio and text.

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… (Read More →)

An activity which may cause an audit record to be reported in an audit trail. The POSIX.6/D13.1 option specifies the audit events corresponding to POSIX.1 interfaces [POSIX.6].

A field within an audit record that identifies the activity reported by the record, and defines the required content of the record [POSIX.6].

An identifier for the individual user accountable for an audit event [POSIX.6].

Information recording security events in the system [ECMA138].

The discrete unit of data reportable in an audit trail on the occurrence of an audit event [POSIX.6].

A field containing information regarding all entities in a transaction, and indicators of the types of processing performed by those entities. [After X9.17/95]

A function that records the security-relevant messages in a security audit trail [10181-7].

A file created by executing statements included in a computer program for the explicit purpose of providing data for auditing.

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… (Read More →)

A function that checks a security audit trail in order to produce, if appropriate, security alarm messages [10181-7].

A function that archives a part of the security audit trail [10181-7].

A function that collects individual audit trail records into a security audit trail [10181-7].

A function that builds security reports out of one or more security audit trails [10181-7].

A function that provides security audit trails according to some criteria [10181-7].

Abbreviation for attachment unit interface.

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°… (Read More →)

1. To establish, usually by challenge and response, that a transmission attempt is authorized and valid.
2. [To] 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 information system (IS), or establish the validity of a transmission. [INFOSEC-99]
3. A challenge given by… (Read More →)

An identity of a principal that has been assured through authentication [10181-2].

1. [Any] Security measure designed to establish the validity of a transmission, message, or originator, or a means of verifying an individual's authorization to receive specific categories of information.
2. A security measure designed to protect a communications system against acceptance of a fraudulent transmission or simulation by establishing the validity of a transmission, message, or originator.
3. Evidence by… (Read More →)

An encryption process or tool in which the results of text encryption depend on all relevant authentication elements. [After X9.24]

An authority recognized in a security domain as a source of certified identities. (See also Subject Authority) [ECMA138].

Authentication information in the form of a security certificate which may be used to assure the identity of an entity guaranteed by an authentication authority [10181-2].

A contiguous group of characters or bits that are corruption-protected by being processed by the authentication algorithm. [After X9.24]

1. A mechanism intended to ensure the identity of an entity by means of an information exchange. [2382-pt.8]
2. A mechanism intended to ensure the identity of an entity by means of information exchange [7498-2].
3. A sequence of one or more transfers of exchange authentication information (AI) for the purposes of performing an authentication[10181-2].

1. Information used to establish the validity of a claimed identity of an entity. [2382-pt.8]
2. Information used to establish the validity of a claimed identity [7498-2].

The entity which starts an authentication exchange [10181-2].

A (data-encryption algorithm) key used to authenticate data in accordance with specific encryption standards. [After X9.26]

A set of rules, part of an access control policy, by which credentials are matched against claims of identity [ECMATR46].

The entity which receives the first transfer of exchange AI in an authentication exchange [10181-2].

[A] cryptosystem or process used for authentication. [INFOSEC-99]

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. [JP 1-02]
2. A letter, numeral, group of letters or numerals, or any combinations of these,… (Read More →)

An entity recognized by some set of secure systems as a trusted source of security information[ECMA138].

1. The rights granted to a user to access, read, modify, insert, or delete certain data, or to execute certain programs.
2. Access privileges granted to a user, program, or process.
3. The granting of access to a security object.
4. The process by which an access control decision is made and enforced.
5. The granting of rights, which includes… (Read More →)

These are mechanisms used to identify, control, and record end-users access to services. These mechanisms are essential components of any online service platform.

Any of several types of attribute certificates containing information used in the authorization process.
Note: Authorization information may also be contained in a public key certificate, in which case that public key certificate also serves as an authorization certification [After X9.45]

A set of rules, part of an access control policy, by which access by security subjects to security objects is granted or denied. An authorization policy may be defined in terms of access control lists, capabilities or attributes assigned to security subjects, security objects or both [ECMATR46].

1. 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]
2. The maximum bandwidth authorized to be used by a station as specified in the station license. This shall be occupied bandwidth or necessary bandwidth, whichever is greater.… (Read More →)

1. A frequency that is allocated and assigned by a competent authority to a specific user for a specific purpose.
2. The frequency, or frequency range, assigned to a station by the Commission [FCC] and specified in the instrument of authorization. [47CFR] Seeassigned frequency.

The highest level issuer of authorization certificates in an organization.
Note: Authorized signatories are designated in a signatory certificate, which is issued to an organization by an agreed signatory authority. [After X9.45]

In security, a user who may, according to an organization's security policy, perform an operation. [After CC-99]

In e-mail systems, a message sent automatically upon receipt of incoming e-mail.
Note: Auto-replies are used to acknowledge delivery of e-mail and to provide receipts for e-mail messages.

Acronym for automatic digital network. See Defense Data Network.

Synonym machine-readable medium.

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… (Read More →)

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… (Read More →)

An automatic, integrated and interconnected maritime communications system serving ship stations on specified inland and coastal waters of the United States. [47CFR]

A radio that can be automatically controlled by electronic devices and that requires little or no human intervention.

Use of automated procedures to ensure security controls are not circumvented or the use of these tools to track actions taken by subjects suspected of misusing the information system (IS). [INFOSEC-99]

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.

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.

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… (Read More →)

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… (Read More →)

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… (Read More →)

A device that enables equipment, such as computers and card dialers, to originate calls automatically over a telecommunications network.

ACG is a code control that is implemented automatically in response to a request from a database to limit traffic. This control can be in the form of six (6) through ten (10) digits. A six-digit control is used to protect the database in instances of a general overload. A ten-digit control is used to control focused overloads.

ACC is a two-part feature. In order for ACC to function properly it must be implemented in the originating and terminating nodes of an interconnected network. The first part enables a (terminating) network node to alert interconnected nodes that it is in Machine Congestion 1 or 2 (MC1 or MC2). The second part allows a distant (originating) network node to… (Read More →)

1. A generalization of automatic data processing to include the aspect of data transfer. [JP1]
2. Combining data processing and data transfer.

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.
2. Data processing by means of one or more devices that use common storage for all or part of a computer… (Read More →)

An assembly of computer hardware, firmware, and software configured for the purpose of classifying, sorting, calculating, computing, summarizing, transmitting and receiving, storing, and retrieving data with a minimum of human intervention [TCSEC].

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.

See automatic calling unit.

Formerly, a worldwide data communications network of the Defense Communications System, now replaced by the Defense Switched Network (DSN).

See error-correcting code.

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.

A device or circuit that maintains the frequency of an oscillator within the specified limits with respect to a reference frequency.

A machine function or series of machine functions controlled by a program and carried out without assistance of an operator.

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.

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).

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),… (Read More →)

Automatic rerouting of the radio portion of a call for signal quality, traffic management, or other reasons. [T1.702-1995]

The automatic display at the PSAP of the caller’s telephone number, the address/location of the telephone and supplementary emergency services information of the location from which a call originates.

A service feature that automatically records data regarding user-dialed calls.

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.

Any organized assembly of resources and methods used to collect, process, and distribute messages largely by automatic means. [JP1]

1. 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.
2. The code that provides the billing number of the line or trunk that originated a call. [T1.104-1988]
3. A system that identifies the billing account for a call. For 911 systems, the ANI… (Read More →)

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.

The process by which a user's location registration is automatically canceled without any explicit action from the user. [T
1. Rpt34-1994]

The process by which a user's location registration is automatically updated without any explicit action from the user. [T
1. Rpt34-1994]

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.

See bootstrap.

[In INFOSEC, a] procedure to rekey a distant crypto-equipment electronically without specific actions by the receiving terminal operator. [INFOSEC-99]
Note: Automatic remote rekeying may also apply to non-crypto devices.

The procedure by which distant equipment is reprogrammed or rekeyed electronically without specific actions by the receiving terminal.

See ARQ.

A circuit providing priority telephone service, typically for key personnel; the circuit is activated when the telephone handset is removed from the cradle causing a ringing signal to be sent to the distant unit(s). See verified off-hook.

Electronic or mechanical selection and routing of outgoing calls without human intervention.

Automatic Scheduled Testing (AST) of Switched Access Services (Feature Groups B, C and D), where the customer provides remote office test lines and 105 test lines with associated responders or their functional equivalent, will consist of monthly loss and C-message noise tests and annual balance test.

A worldwide, switched, secure voice network developed to fulfill DOD long-haul, secure voice requirements. [JP1]

A service feature in which the terminals at each of a set of specified addresses are automatically connected, in a predetermined sequence, to a single terminal at a specified address.

Synonym hotline.

The testing of selected channels or paths by providing a very brief beacon-like identifying broadcast that may be used by other stations to evaluate connectivity, propagation, and availability, and to identify known working channels for possible later use for communications or calling.
Note 1: Automatic soundings are primarily intended to increase the efficiency of the automatic link establishment (ALE) function,… (Read More →)

1. In data communications, a switching system in which all the operations required to execute the three phases of information-transfer transactions are automatically executed in response to signals from a user end-instrument.
Note: In an automatic switching system, the information-transfer transaction is performed without human intervention, except for initiation of the access phase and the disengagement phase by a user.… (Read More →)

Formerly, the principal long-haul, unsecure voice communications network within the Defense Communications System, now replaced by the Defense Switched Network (DSN).

1. The implementation of processes by automatic means. [JP 1-02]
2. The investigation, design, development, and application of methods of rendering processes automatic, self-moving, or self-controlling.
3. The conversion of a procedure, a process, or equipment to automatic operation. [JP 1-02]

Internet (TCP/IP) terminology for a collection of gateways (routers) that fall under one administrative entity and that cooperate using a common interior gateway protocol (IGP). [Bahorsky]
Note: Routers pertaining to different autonomous systems must agree on a common exterior gateway protocol in order to communicate with each other effectively.

Acronym for Automatic Secure Voice Communications Network.

Acronym for Automatic Voice Network. Superseded byDefense Switched Network.

An offline operation performed by equipment not under control of the processing unit.

Electric power that is provided by an alternate source and that serves as backup for the primary power source at the station main bus or prescribed sub-bus.
Note 1: An offline unit provides electrical isolation between the primary power source and the critical technical load whereas an online unit does not.
Note 2: A Class A power source is a… (Read More →)

1. Storage that is available to a processor only through its input/output channels.
2. In a computer, any storage that is not internal memory, i.e., is not random access memory (RAM).
Note: Examples of auxiliary storage media are magnetic diskettes, optical disks including CD ROM, and magnetic tape cassettes.

Audio Video

1. The degree to which a system, subsystem, or equipment is operable and in a committable state at the start of a mission, when the mission is called for at an unknown, i.e., a random, time.
Note 1: The conditions determining operability and committability must be specified.
Note 2: Expressed mathematically, availability is 1 minus the unavailability.
2. The ratio… (Read More →)

1. In voice, video, or data communications, a circuit between two points that is ready for service, but is in the idle state.
2. In facsimile transmission, the portion of the scanning line that can be specifically used for image signals. Synonym useful line.

Available numbers are numbers that are available for assignment to subscriber access lines, or their equivalents, within a switching entity or point of interconnection and are not classified as assigned, intermediate, administrative, aging, or reserved. Available numbers is a residual category that can be calculated by subtracting a sum of numbers in the assigned, reserved, intermediate, aged, and administrative primary… (Read More →)

A state where a (bidirectional or unidirectional) service is usable.
Note: Each direction of a service is assumed to be in the available state unless a transition to the unavailable state is observed without a subsequent transition to the available state. In this standard the transitions between the available and unavailable states are: (a) transition to the unavailable state occurs… (Read More →)

From the point of view of a user, the time during which a functional unit can be used.
Note: From the point of view of operating and maintenance personnel, the available time is the same as the uptime, i.e., the time during which a functional unit is fully operational.

A current-multiplying phenomenon that occurs in a semiconductor photodiode that is reverse-biased just below its breakdown voltage.
Note: Under such a condition, photocurrent carriers, i.e., electrons, are swept across the junction with sufficient energy to ionize additional bonds, creating additional electron-hole pairs in a regenerative action. [After FAA]

A photodiode that operates with a reverse-bias voltage that causes the primary photocurrent to undergo amplification by cumulative multiplication of charge carriers.
Note: As the reverse-bias voltage increases toward the breakdown, hole-electron pairs are created by absorbed photons. An avalanche effect occurs when the hole-electron pairs acquire sufficient energy to create additional pairs when the incident photons collide with the… (Read More →)

An interactive representation of a human in a virtual reality environment. [Bahorsky]

1. Advanced Video Codec;
2. Advanced Video Coding

In video systems, the average level of the picture signal during active scanning time integrated over a frame period; defined as a percentage of the range between blanking and reference white level.

Synonym effective transmission rate.

Abbreviation for audio video interleaved. A file-name extension used to indicate a compressed video file in the AVI standard for a common operating system.
Note: This file format for digital video and audio compression indicates that (a) the audio and video data are stored in alternate blocks, and (b) the file format is cross-platform compatible, allowing . avi video files… (Read More →)

Abbreviation for audio video kernel. Digital video interface (. dvi) software designed for playing motion video and audio across several different varieties of hardware and operating systems. [After Silicon]

The assignment of a circuit path to avoid certain critical or trouble-prone circuit nodes.

Abbreviation for audio-video support system. A digital video interface system software (for DOS) that plays motion video and audio. [After Silicon]

Abbreviation for American wire gauge. A standard system for measuring and classifying the thickness of wire conductors; also referred to as the "Brown and Sharpe (B & S)" wire gauge.

Abbreviation for additive white gaussian noise. See white noise.

In an optical fiber, the propagation constant evaluated along the optical axis of the fiber in the direction of transmission.
Note: The real part of the axial propagation constant is the attenuation constant. The imaginary part is the phase constant. [After 2196]

Of an electromagnetic wave having elliptical polarization, the ratio of the magnitudes of the major axis and the minor axis of the ellipse described by the electric field vector.

A light ray that travels along the optical axis.