Abbreviation for numerical aperture.

Used in thousands-block number pooling to describe a reservoir of unassigned thousands-blocks administered by the Pooling Administrator for purposes of assignment to certified service providers participating in thousands-block number pooling.

Abbreviation for signal-plus-noise-to-noise ratio.

A logical administrative domain interacting with the networks, HW devices, SW components, protocols, and data infrastructure as required for proper Service operation, management, and billing.

Also known as Home Network End-Devices (HNED), Home Network Device (HND), Consumer Equipment (CE), terminal, and physical device. A piece of HW equipment running its SW and attached to a Home Network and being identified by a GUID - e.g., a MAC address. A single Device can be used by one or more Users.

1. A top-level domain name-suffix originally intended to designate commercial entities such as corporations and companies.
2. A filename suffix indicating an executable file.
Note: Usually, ". com" programs are smaller and simpler than programs with the ". exe" suffix.

Abbreviation for file name extension. A label that identifies an enhanced text file format used by some digests and electronic publications. [Bahorsky]

A file-name extension that identifies a Motion Picture Experts Group (MPEG) audio file. [Bahorsky]

The computer file-name extension that identifies a Motion Picture Experts Group (MPEG) video file. See M-PEG. [Bahorsky]

See M-PEG.

See M-PEG.

A computer file name extension that identifies a Motion Picture Experts Group (MPEG) video file. See M-PEG. [Bahorsky]

A file extension name for one format [ i.e., a wave format] of a sound file. [Source: http://www. webwords. net/html/_p_. html]

A feature of the North American Numbering Plan that identifies customer dialed calls that are operator assisted, either by electronic or manual (human) means. [After T1.401-1988]

Abbreviation for zero transmission level point.

10/100 Mbps baseband twisted-pair (Ethernet)

In telephony, a noise weighting used in a noise measuring set to measure line noise as it would be perceived if the line were terminated with a No.144-receiver, or a similar instrument.
Note: The meter scale readings are in dBrn (144-line).

In telephony, a noise weighting used in a noise measuring set to measure noise across the receiver of an instrument equipped with a No.144-receiver.
Note: The meter scale readings are in dBrn (144-receiver).

Single Carrier Radio Transmission Technology.

2.5nd Generation Wireless

2nd Generation

3rd Generation

3rd Generation Partnership Project

3rd Generation Partnership Project, 2

Third Generation GSM Services

50-Gigabit-capable Passive Optical Network

The main operations support system used to create and update Toll Free records that are then downloaded to Service Control Points (SCPs) or RouteLink for processing Toll Free Service calls. The system is used by Resp Orgs to manage and administer SMS/800 records.

An entity designated under state law or regulation to have decision-making and oversight responsibilities for a 9-1-1 Emergency Number System for one or more PSAPs.

A carrier access code for obtaining switched access to interchange carriers where (a) the calling customer accesses the IC and passes the address information, if any, in two distinct operations; (b) the calling customer usually uses in-band signals to pass the address, if any, to the IC; and (c) the EC does not repeat the address information.
Note: The X… (Read More →)

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.

Abbreviation for bit.

Abbreviation for bel, byte.

1. A communications channel used for the transmission of an aggregate signal generated by multichannel transmitting equipment.
2. The CCITT (now, ITU-T) designation for a clear channel, 64-kb/s service capability provided to a subscriber under the Integrated Services Digital Network offering.
Note: The B channel, also called the bearer channel, is intended for transport of user information, as opposed to… (Read More →)

An MPEG video frame type that provides bidirectional interframe compression.
Note: A b frame derives its content from the closest 1 or P frame, one in the past and one in the future. Generating b frames requires greater computing power than does generating 1 or P frames. The use of b frames enables compression ratios of 200:
1. Robust MPEG… (Read More →)

Billing and Customer Care

Abbreviation for broadband ISDN.

Abbreviation for bits per second.

Business to Business

Back-to-Back User Agreements

Business to Consumer

Abbreviation for bipolar with three-zero substitution. A T-carrier line code in which bipolar violations are deliberately inserted if user data contain a string of 3 or more consecutive zeros.
Note 1: B3ZS is used to ensure a sufficient number of transitions to maintain system synchronization when the user data stream contains an insufficient number of "ones" to do so.
Note… (Read More →)

Abbreviation for bipolar with six-zero substitution. A T-carrier line code in which bipolar violations are deliberately inserted if user data contain a string of 6 or more consecutive zeros. A code in which eight consecutive zeros are replaced with the sequence 000+-0-+ if the preceding pulse was + and with the sequence 000-+0+- of the preceding pulse was -, where… (Read More →)

Abbreviation for bipolar with eight-zero substitution. A T-carrier line code in which bipolar violations are deliberately inserted if user data contains a string of 8 or more consecutive zeros.
Note 1: B8ZS is used to ensure a sufficient number of transitions to maintain system synchronization when the user data stream contains an insufficient number of "ones" to do so.
Note… (Read More →)

In transmission systems, the aggregate of crosstalk induced in a given line by all other lines.

Synonym trapdoor.

1. A direct connection between the output of a transmitting device and the input of an associated receiving device.
Note: When used for equipment measurements or testing purposes, such a back-to-back connection eliminates the effects of the transmission channel or medium.
2. A direct connection between the output of a receiving device and the input to a transmitting device.
Note:… (Read More →)

1. The high-traffic-density connectivity portion of any communications network.
2. In packet-switched networks, a primary forward-direction path traced sequentially through two or more major relay or switching stations.
Note: In packet-switched networks, a backbone consists primarily of switches and interswitch trunks.

1. In Web pages, an image or color, usually defined in HTML, that serves as the underlying color or imagery for a Web page.
Note: Browsers may also be configured to dictate backgrounds.
2. In computer display systems, the underlying color or imagery for the main screen or for the fundamental window of a computer's operating system.

The total system noise in the absence of information transmission.

The execution of lower priority computer programs when higher priority programs are not using the system resources.
Note: Priorities may be assigned by system software, application software, or the operator.

1. The practice of routing telecommunications traffic beyond its intended destination, and then back to the intended destination, usually for the purpose of taking advantage of tariffs or prices that are lower than those afforded by direct routing.
2. In security, to bring a call that has been routed along a particular path (usually via satellite) to some earlier position… (Read More →)

1. Radio wave propagation in which the direction of the incident and scattered waves, resolved along a reference direction (usually horizontal) are oppositely directed. A signal received by backscattering is often referred to as "backscatter. " [JP 1-02]
2. In optics, the scattering of light into a direction generally opposite to the original one.

1. [A] copy of files and programs made to facilitate recovery, if necessary. [INFOSEC-99]
2. See backup file.

A copy of a file made for purposes of later reconstruction of the file, if necessary.
Note: A backup file may be used for preserving the integrity of the original file and may be recorded on any suitable medium. Synonym job-recovery control file.

1. In data transmission, a secondary channel in which the direction of transmission is constrained to be opposite to that of the primary, i.e., the forward (user-information) channel.
Note: The direction of transmission in the backward channel is restricted by the control interchange circuit that controls the direction of transmission in the primary channel.
2. In a data circuit, the… (Read More →)

A signal unit (or sequence of bits) that (by changing its status) is used to request retransmission by the remote end whenever it receives a signal unit that is out of sequence. [T1.226-1992]

The reconstruction of an earlier version of a file by using a newer version of data recorded in a journal.

A field in a signal unit that contains the forward sequence number of a correctly received signal unit being acknowledged in the signal unit that is being returned to the sender. [After T1.226-1992]

A signal sent from the called to the calling station, i.e., from the original data sink to the original data source.
Note: Backward signals are usually sent via a backward channel and may consist of supervisory, acknowledgment, or control signals.

The use of supervisory signal sequences from a secondary to a primary station.

Building Automation and Control Network

A program that attempts to propagate itself by e-mailing a copy of itself to e-mail addresses found on a recipient's hard drive. This is done without the consent or knowledge of the recipient.
Note: In many cases, this type of program does not attempt to cause any direct damage to user's system, but rather attempts to overload the e-mail distribution… (Read More →)

A technique for copy protection in which bad sectors are intentionally written on a diskette. [2382-pt.8]

In electrical circuits and networks, to adjust the impedance to achieve specific objectives, such as to reach specified return loss objectives at a hybrid junction of two-wire and four-wire circuits.

1. A measure of the degree of balance between two impedances connected to two conjugate sides of a hybrid set, coil, network, or junction.
2. A measure of the effectiveness with which a balancing network simulates the impedance of a two-wire circuit at a hybrid coil.

Pertaining to electrical symmetry.

1. In PCM systems, a code constructed so that the frequency spectrum resulting from the transmission of any code word has no dc component.
2. In PCM, a code that has a finite digital sum variation.

A transmission line consisting of two conductors in the presence of ground, capable of being operated in such a way that when the voltages of the two conductors at all transverse planes are equal in magnitude and opposite in polarity with respect to ground, the currents in the two conductors are equal in magnitude and opposite in direction.
Note: A… (Read More →)

A modulator constructed so that the carrier is suppressed and any associated carrier noise is balanced out.
Note 1: The balanced modulator output contains only the sidebands.
Note 2: Balanced modulators are used in AM transmission systems.

Synonym balanced line.

1. In a hybrid set, hybrid coil, or resistance hybrid, a circuit used to match, i.e., to balance, the impedance of a uniform transmission line, i.e., twisted metallic pair, over a selected range of frequencies.
Note: A balancing network is required to ensure isolation between the two ports of the four-wire side of the hybrid.
2. A device used between… (Read More →)

Abbreviation for balanced to unbalanced. In radio frequency usage, a device used to couple a balanced device or line to an unbalanced device or line.

1. In communications, the frequency spectrum between two defined limits.
2. A group of tracks on a magnetic drum or on one side of a magnetic disk.
3. A set of frequencies authorized for use in a geographical area defined for common carriers for purposes of communications system management.

Synonym band-stop filter.

Synonym band-stop filter.

A filter that attenuates, usually to very low levels, all frequencies between two non-zero, finite limits and passes all frequencies not within the limits.
Note: A band-stop filter may be designed to stop the specified band of frequencies but usually only attenuates them below some specified level. Synonyms band-elimination filter, band-rejection filter, band-suppression filter, notched filter.

Synonym band-stop filter.

A filter that ideally passes all frequencies between two non-zero finite limits and bars all frequencies not within the limits.
Note: The cutoff frequencies are usually taken to be the 3-dB points.

A device that imposes hard limiting on a signal and contains a filter that suppresses the unwanted products (harmonics) of the limiting process.

1. The difference between the limiting frequencies within which performance of a device, in respect to some characteristic, falls within specified limits.
2. The difference between the limiting frequencies of a continuous frequency band.
3. A characteristic of a communication channel that is the amount of information that can be passed through it in a given amount of time, usually… (Read More →)

1. The lowest modulation frequency at which the RMS peak-to-valley amplitude (optical power) difference of an intensity-modulated monochromatic signal decreases, at the output of the fiber, to a specified fraction (usually one-half) of the RMS peak-to-valley amplitude (optical power) difference of a nearly-zero (arbitrarily low) modulation frequency, both modulation frequencies having the same RMS peak-to-valley amplitude (optical power) difference at… (Read More →)

In a distributed-queue dual-bus network, a procedure in which a node occasionally skips the use of empty queued arbitrated slots, and which procedure effects sharing of the bandwidth mechanisms.

1. The reduction of the bandwidth needed to transmit a given amount of data in a given time.
2. The reduction of the time needed to transmit a given amount of data in a given bandwidth.
Note: Bandwidth compression implies a reduction in normal bandwidth of an information-carrying signal without reducing the information content of the signal.

The condition prevailing when the system bandwidth limits performance.
Note: Bandwidth-limited operation occurs when the system distorts the signal waveform beyond specified limits. For linear systems, bandwidth-limited operation is equivalent to distortion-limited operation.

Of an optical fiber, under specified launching and cabling conditions, at a specified wavelength, a figure of merit equal to the product of the fiber's length and the 3-dB bandwidth of the optical signal.
Note 1: The bandwidth•distance product is usually stated in megahertz•kilometer (MHz•km) or gigahertz•kilometer (GHz•km).
Note 2: The bandwidth•distance product, which is normalized to 1 km, is… (Read More →)

Synonym for bandwidth•distance product.

The exclamation point character (!) used in early addressing schemes to separate the names of individual machines.
Note: Bang-style addressing is no longer common. Synonym scream.

1. An HTML tag that creates scrolling text on a Web page. [Bahorsky]
2. Scrolling or fixed text used as an advertisement on a Web page, e.g., banner advertising. [Bahorsky]
3. In computer networking, a page that is automatically prefixed to, and printed out as part of, a printing job , as a means of identifying uniquely the output belonging… (Read More →)

Synonym banner.

A code representing characters by sets of parallel bars of varying thickness and separation that are read optically by transverse scanning.
Note: Bar code uses include identifying merchandise, sorting mail, and inventorying supplies.

Jamming accomplished by transmitting a band of frequencies that is large with respect to the bandwidth of a single emitter.
Note: Barrage jamming may be accomplished by presetting multiple jammers on adjacent frequencies or by using a single wideband transmitter. Barrage jamming makes it possible to jam emitters on different frequencies simultaneously and reduces the need for operator assistance or… (Read More →)

1. In the numeration system commonly used in scientific notation, the real number that is raised to a power denoted by the exponent and then multiplied by the coefficient to determine the value of the number represented without the use of exponents.
Note: An example of a base is the number
6. 25 in the expression
2. 70 ×
6.… (Read More →)

1. An address that is used as the origin in the calculation of addresses in the execution of a computer program. [From Weik '96]
2. A given address from which an absolute address is derived by combination with a relative address.
Note: Base addresses are primarily used by computer programmers rather than by computer users. [From Weik '96]

Communications services, such as the installation, operation, maintenance, augmentation, modification, and rehabilitation of communications networks, systems, facilities, and equipment, including off-post extensions, provided for the operation of a military post, camp, installation, station, or activity. Synonym communications base station.

An Earth station in the fixed-satellite service or, in some cases, in the land mobile-satellite service, located at a specified fixed point or within a specified area on land to provide a feeder link for the land mobile-satellite service. [NTIA] [RR] [47CFR]

A key used to derive (to compute cryptographically) or to decrypt transaction keys. [After X9.24]

A standard or specification that is recognized as appropriate for normative reference in a profile by the body adopting that profile, but is not a profile itself [POSIX.0].

1. A land station in the land mobile service. [NTIA] [RR] [47CFR]
2. In personal communication service, the common name for all the radio equipment located at one fixed location, and that is used for serving one or several cells.

1. The original band of frequencies produced by a transducer, such as a microphone, telegraph key, or other signal-initiating device, prior to initial modulation.
Note 1: In transmission systems, the baseband signal is usually used to modulate a carrier.
Note 2: Demodulation re-creates the baseband signal.
Note 3: Baseband describes the signal state prior to modulation, prior to multiplexing, following… (Read More →)

A local area network in which information is encoded, multiplexed, and transmitted without modulation of carriers.

Intensity modulation of an optical source, e.g., LED or ILD, directly, without first modulating the signal of interest onto an electrical carrier wave. [After FAA]

Transmission of a digital or analog signal at its original frequencies; i.e., a signal in its original form, not changed by modulation.

Abbreviation for base communications.

A characterization of a simple standardized combination of access channels that constitute the access arrangements for the majority of ISDN users; specifically, any of the following combinations of access channels: (1) one D-channel, (2) one B-channel plus one D-channel, (3) two B-channels plus one D-channel. [After T1.601-1988]

A call between two users that does not include additional features (e.g., a plain telephone call).

The sequence of activities used in processing a basic call attempt. [T1.667-1999]

A component that is identifiable at the lowest hierarchical level of specification produced during Detailed Design [ITSEC].

A commercial service that can extend telephone service to rural areas by replacing the local loop with radio communications.
Note: In the BETRS, non-government ultra high frequency (UHF) and very high frequency (VHF) common carrier and the private radio service frequencies are shared.

See group.

Control of data links by use of the control characters of the 7-bit character set for information processing interchange as given in ISO Standard 646-1983 and CCITT (ITU-T) Recommendation V.3-1972.

An ITU-T Integrated Services Digital Network (ISDN) multipurpose user interface standard that denotes the capability of simultaneous voice and data services provided over two clear 64-kb/s channels and one clear 16-kb/s channel (2B+D) access arrangement to each user location.

1. A pure transmission capability over a communication path that is virtually transparent in terms of its interaction with customer-supplied information.
2. The offering of transmission capacity between two or more points suitable for a user's transmission needs and subject only to the technical parameters of fidelity and distortion criteria, or other conditioning.

1. An optional unbundled feature, generally associated with the basic serving arrangement (BSA), that an enhanced-service provider (ESP) may require or find useful in configuring an enhanced service.
2. A fundamental (basic) communication network service; an optional network capability associated with a BSA.
Note: BSEs constitute optional capabilities to which the customer may subscribe or decline to subscribe.

1. The fundamental tariffed switching and transmission (and other) services that an operating company must provide to an enhanced service provider (ESP) to connect with its customers through the company network.
2. In an open-network-architecture context, the fundamental underlying connection of an enhanced service provider (ESP) to and through the operating company's network including an ESP access link, the features… (Read More →)

In data transmission, the status of the capability of a secondary station to send or receive a frame containing an information field.

1. A host computer that, in a screened subnetwork, performs the functions of a firewall. Synonym screened-host gateway. [2382-pt.35]
2. A computer system that must be highly secured because it is vulnerable to attack, usually because it is exposed to the Internet and is a main point of contact for users of internal networks. It gets its name from the… (Read More →)

1. The processing of data or the accomplishment of jobs accumulated in advance in such a manner that the user cannot further influence the processing while it is in progress.
2. The processing of data accumulated over a period of time.
3. Loosely, the execution of computer programs serially.
4. Pertaining to the technique of executing a set of computer… (Read More →)

Synonym batched transmission.

The transmission of two or more messages from one station to another without intervening responses from the receiving station. Synonym batched communications.

1. A unit of modulation rate.
Note: One baud corresponds to a rate of one unit interval per second, where the modulation rate is expressed as the reciprocal of the duration in seconds of the shortest unit interval.
2. A unit of signaling speed equal to the number of discrete signal conditions, variations, or events per second.
Note 1: If… (Read More →)

A synchronous code in which five equal-length bits represent one character.
Note 1: The Baudot code, which was developed circa 1880, has been replaced by the start-stop asynchronous International Alphabet No.2 (IA No.2).
Note 2: IA No.2 is not, and should not be identified as, the Baudot code.
Note 3: The Baudot code has been widely used in teletypewriter systems.

broadband.

Broadband Equipment

Baseband Unit

Abbreviation for block check character.

Abbreviation for binary-coded decimal code. See binary-coded decimal notation.

Broadband Content Guide

Abbreviation for Bose-Chaudhuri-Hochquenghem code. A multilevel, cyclic, error-correcting, variable-length digital code used to correct errors up to approximately 25% of the total number of digits.
Note: BCH codes are not limited to binary codes, but may be used with multilevel phase-shift keying whenever the number of levels is a prime number or a power of a prime number, such as… (Read More →)

Abbreviation for bit-count integrity.

Abbreviation for baud.

Border Element

See radiobeacon station.

1. The main lobe of an antenna radiation pattern.
2. A column of light.
Note: A beam may be parallel, divergent, or convergent. [After FAA]

Of an electromagnetic beam, along any specified line that (a) intersects the beam axis and (b) lies in any specified plane normal to the beam axis, the distance between the two diametrically opposite points at which the irradiance is a specified fraction, e.g., ½ or 1/, of the beam's peak irradiance.
Note 1: Beam diameter is usually used to characterize… (Read More →)

Of an electromagnetic beam, in any plane that intersects the beam axis, the increase in beam diameter with distance from the aperture from which the beam emerges.
Note 1: Beam divergence is usually used to characterize electromagnetic beams in the optical regime, i.e., cases in which the aperture from which the beam emerges is very large with respect to the… (Read More →)

Changing the direction of the main lobe of a radiation pattern.
Note: In radio systems, beam steering may be accomplished by switching antenna elements or by changing the relative phases of the rf signals driving the elements. In optical systems, beam steering may be accomplished by changing the refractive index of the medium through which the beam is transmitted or… (Read More →)

A device for dividing an optical beam into two or more separate beams.
Note: An example of a beamsplitter is a partially reflecting mirror.

1. In the radio regime, of an antenna pattern, the angle between the half-power (3-dB) points of the main lobe, when referenced to the peak effective radiated power of the main lobe.
Note: Beamwidth is usually expressed in degrees. It is usually expressed for the horizontal plane, but may also be expressed for the vertical plane.
2. For the optical… (Read More →)

See B channel.

A telecommunications service that allows transmission of user-information signals between user-network interfaces. See B channel, service access.

See heterodyne.

Synonym paging, radio paging.

A unit of measure of ratios of power levels, i.e., relative power levels.
Note 1: The number of bels for a given ratio of power levels is calculated by taking the logarithm, to the base 10, of the ratio. Mathematically, the number of bels is calculated as B = log10(P1/P2) where P1 and P2 are power levels.
Note 2: The… (Read More →)

A transmission control character that is used when there is a need to call for user or operator attention in a communications system, and that usually activates an audio or visual alarm or other attention-getting device.

Historically, any of the 22 operating companies that were divested from AT&T by court order.
Note: Cincinnati Bell Telephone Co. and Southern New England Bell Telephone Co. were not included.

1. [A] formal state-transition model of a computer security policy that describes a formal set of access controls based on information sensitivity and subject authorizations. [INFOSEC].
2. A formal state transition model of computer security policy that describes a set of access control rules. In this formal model, the entities in a computer system are divided into abstract sets of… (Read More →)

See macrobend loss, microbend loss.

[In INFOSEC a] condition of cryptographic data that cannot be compromised by human access. [INFOSEC-99]

[In security, a] nonhostile environment that may be protected from external hostile elements by physical, personnel, and procedural security countermeasures. [INFOSEC-99]

1. Bit Error Rate,
2. Bit Error Ratio.

Acronym for bit error ratio tester.

A secondary software product test involving select or voluntary participants before the product is marketed to the general public.
Note: Participants agree to provide detailed feedback to the product's manufacturer in return for their being allowed to preview, use, and contribute to the final form of the product. [After Bahorsky]

Abbreviation for basic exchange telecommunications radio service.

Unauthorized access to a momentarily inactive terminal, of a legitimate user, assigned to a communications channel.

Abbreviation for broadband exchange.

1. Breakout Gateway Call Function;
2. Border Gateway Control Function

Border Gateway Protocol

Abbreviation for binary synchronous (bi-sync) communication.

1. A systematic deviation of a value from a reference value.
2. The amount by which the average of a set of values departs from a reference value.
3. Electrical, mechanical, magnetic, or other force (field) applied to a device to establish a reference level to operate the device.
4. In telegraph signaling systems, the development of a positive or… (Read More →)

1. Signal distortion resulting from a shift in the bias.
2. In binary signaling, distortion of the signal in which all the significant intervals have uniformly longer or shorter durations than their theoretical durations.
Note: Bias distortion is expressed in percent of the system-specified unit interval.

In the generation of pseudorandom or random numbers, pertaining to or describing a condition that renders the more likely occurrence of some numbers or patterns than others. [After X9.17]

Bearer Independent Call Control

An antenna consisting of two conical conductors, having a common axis and vertex, and extending in opposite directions.
Note 1: In a biconical antenna, excitation is applied at the common vertex.
Note 2: If one of the cones is reduced to a plane, the antenna is called a discone.

In data transmission, the condition that exists when information flow characteristics are different in each direction.

Association established between two higher layer entities for which information is transmitted between both entities. [After T1.629-1999]

See directional coupler.

The condition that exists when information flow characteristics are the same in each direction.

A format for transmission or storage of binary data in which the most significant byte (bit) appears first. [After X9.42]

French abbreviation for International Time Bureau. See International Atomic Time.

Synonym bilateral synchronization.

A synchronization control system between exchanges A and B in which the clock at exchange A controls the data received at exchange B and the clock at exchange B controls the data received at exchange A.
Note: Bilateral synchronization is usually implemented by deriving the timing from the incoming bit stream. Synonym bilateral control.

An array of parallel dipole antennas with flat reflectors, usually positioned in a line or plane.
Note 1: The spacing and dimensions of the dipoles depend on the wavelength.
Note 2: The main lobe of a fixed billboard antenna may, within limits, be steered by appropriate phasing of the respective signals to individual elements of the array. Synonym broadside antenna.

Binary MPEG format for XML

Binary

1. Pertaining to a selection, choice, or condition that has two possible different values or states.
2. Pertaining to a fixed radix numeration system that has a radix of 2.

A code, the elements of which can assume either one of two possible states.

See bit.

A constituent element of data that takes either of two values or states.
Note: Binary element should not be confused with binary digit.

See truncated binary exponential backoff.

The process of varying a parameter of a carrier as a function of two finite, discrete states.

1. Any notation that uses two different characters, usually the digits 0 and
1.
Note: Data encoded in binary notation need not be in the form of a pure binary numeration system; e.g., they may be represented by a Gray code.
2. A scheme for representing numbers, which scheme is characterized by the arrangements of digits in sequence, with the… (Read More →)

A number that is expressed in binary notation and is usually characterized by the arrangement of bits in sequence, with the understanding that successive bits are interpreted as coefficients of successive powers of the base
2.

Synonym bit string.

A character-oriented, data-link-layer protocol.
Note: The bi-sync protocol is being phased out of most computer communication networks in favor of bit-oriented protocols such as SDLC, HDLC, and ADCCP.

Pertaining to the representation of a decimal digit by a unique arrangement of no fewer than four binary digits.

A binary notation in which each of the decimal digits is represented by a binary numeral. Synonyms binary-coded decimal code, binary-coded decimal representation.

Synonym binary-coded decimal notation.

See binary-coded decimal notation.

Synonym binary-coded decimal notation.

1. In computer, communications, and automatic data processing systems, assigning a value or referent to an identifier.
Note: Examples of binding include assigning a value to a parameter, assigning an absolute address to a virtual or relative address, and assigning a device identifier to a symbolic address or label.
2. [In security, the] process of associating a specific communications terminal… (Read More →)

An aspect of the assessment of the effectiveness of a Target of Evaluation, namely the ability of its security enforcing functions and mechanisms to work together in a way which is mutually supportive and provides an integrated and effective whole [ITSEC].

Any specific and uniquely identifiable physical human characteristic, e.g., of the retina, iris, acoustic spectrum of the voice (i.e., voiceprint), fingerprint(s), handwriting, pattern of finger lengths, etc. , that may be used to validate the identity of an individual.
Note: Biometrics provide a highly secure means of identification, for purposes of security involving, e.g., Internet communications and cryptosystems.

[In INFOSEC] automated methods of authenticating or verifying an individual based upon a physical or behavioral characteristic. [INFOSEC-99]

Synonym phase-shift keying.

1. A signal that may assume either of two polarities, neither of which is zero.
Note 1: A bipolar signal may have a two-state non-return-to-zero (NRZ) or a three-state return-to-zero (RZ) binary coding scheme.
Note 2: A bipolar signal is usually symmetrical with respect to zero amplitude, i.e., the absolute values of the positive and negative signal states are nominally… (Read More →)

In a bipolar alternate mark inversion (AMI) signal, a "one" condition (mark, pulse) having the same polarity as its predecessor. [After T1.408-1990]

In a transparent material, anisotropism of the refractive index, which varies as a function of polarization as well as orientation with respect to the incident ray.
Note 1: The term "birefringence" means, literally, "double refraction. "
Note 2: All crystals except those of cubic lattice structure exhibit some degree of anisotropy with regard to their physical properties, including refractive index.… (Read More →)

See birefringence.

The phenomenon stating that, for a category size of 365 (the number of days in a year), after only 23 people are gathered, the probability is greater than
0. 5 that at least two people have a common birthday (month and day).
Note: The birthday phenomenon applied to DES encryption means that where category size is 264, this same probability… (Read More →)

Pertaining to a device capable of assuming either one of two stable states.

Synonym flip-flop.

Synonym flip-flop.

Synonym flip-flop.

1. Abbreviation forbinary digit.
1. A character used to represent one of the two digits in the numeration system with a base of two, and only two, possible states of a physical entity or system.
2. In binary notation either of the characters 0 or
1.
3. A unit of information equal to one binary decision or the designation of… (Read More →)

The sequence of bits used to encode a character.

The number of bits recorded per unit length, area, or volume.
Note: Bit density is the reciprocal of bit pitch. Synonym recording density.

Synonym bits per pixel.

A bit that is transferred from the source to the destination within the assigned time slot, but that, when delivered, is of a different value from that sent from the source. [After T1.503-1989] [After T1.507-1996]

Deprecated term. See bit error ratio.

A test performed on a digital facility/service which counts erroneous bits and divides them by the bits sent over a set period of time. Usually expressed as a power of 10 e. g. (1 x $ 10 sup -6 $).

1. The number of erroneous bits divided by the total number of bits transmitted, received, or processed over some stipulated period.
Note 1: Examples of bit error ratio are (a) transmission BER, i.e., the number of erroneous bits received divided by the total number of bits transmitted; and (b) information BER, i.e., the number of erroneous decoded (corrected) bits divided… (Read More →)

A testing device that compares a received data pattern with a known transmitted pattern to determine the level of transmission quality.

A method of error monitoring. If even parity is used, an N bit code is generated by the transmitting equipment over a specified portion of the signal in such a manner that the first bit of the code provides even parity over the first bit of all N-bit sequences in the covered portion of the signal, the second bit provides… (Read More →)

See bit, character interval, unit interval.

1. The changing of the state of a bit to the opposite state.
2. The changing of the state that represents a given bit, i.e., a 0 or a 1, to the opposite state.
Note: For example, if a 1 is represented by a given polarity or phase at one stage in a circuit, the 1 is represented by the… (Read More →)

In embedded ADPCM (adaptive differential pulse-code modulation), the process of discarding the enhancement bits. [T1.310-1991]

The practice of establishing, within a code set, a number of subsets that have an identical bit representation except for the state of a specified bit.
Note: An example of bit pairing occurs in the International Alphabet No.5 and the American Standard Code for Information Interchange (ASCII), where the upper case letters are related to their respective lower case letters… (Read More →)

The amount of time required to transmit a logical one or a logical zero. [T1.106-1988]

A character position in a word in a binary notation.

1. In a bit stream, the number of bits occurring per unit time, usually expressed in bits per second.
Note: For n-ary operation, the bit rate is equal to log2n times the rate (in bauds), where n is the number of significant conditions in the signal.
2. The rate of transmission of information in binary (two state) form in bits… (Read More →)

In digital carrier systems, the practice or technique of preempting, at regular intervals and for the purpose of transmitting signaling information, one digit time slot that (a) is associated with the given user channel for which signaling is required, and (b) is used primarily for transporting encoded speech via that channel.
Note 1: Bit robbing is an option in networks… (Read More →)

In digital transmission, the loss of a bit or bits, caused by variations in the respective clock rates of the transmitting and receiving devices.
Note: One cause of bit slippage is overflow of a receive buffer that occurs when the transmitter's clock rate exceeds that of the receiver. This causes one or more bits to be dropped for lack of… (Read More →)

A sequence of bits.
Note: In a bit stream, individual bit strings may be separated by data delimiters. Synonym binary string.

The insertion of noninformation bits into data.
Note 1: Stuffed bits should not be confused with overhead bits.
Note 2: In data transmission, bit stuffing is used for various purposes, such as for synchronizing bit streams that do not necessarily have the same or rationally related bit rates, or to fill buffers or frames. The location of the stuffing bits… (Read More →)

See nominal bit stuffing rate.

Synchronization in which the decision instant is brought into alignment with the received bit, i.e., the basic signaling element.

Operation in which data circuit terminating equipment (DCE), data terminal equipment (DTE), and transmitting circuits are all operated in bit synchronism with a clock.
Note 1: In bit synchronous operation, clock timing is usually delivered at twice the modulation rate, and one bit is transmitted or received during each clock cycle.
Note 2: Bit synchronous operation is sometimes erroneously referred… (Read More →)

In data transmission, an operation in which manual, semiautomatic, or automatic shifts in the data modulation rate are accomplished by gating or slewing the clock modulation rate.
Note: For example, bit-by-bit asynchronous operation may be at 50 b/s one moment and at 1200 b/s the next moment.

1. In message communications, the preservation of the exact number of bits that are in the original message.
2. In connection-oriented services, preservation of the number of bits per unit time.
Note: Bit-count integrity is not the same as bit integrity, which requires that the delivered bits correspond exactly with the original bits.

See bandwidth•distance product.

A characteristic of some digital data transmission systems that impose no restrictions on, or modification of, the transmitted bit sequence.
Note: Bit-sequence-independent protocols are in contrast to protocols that reserve certain bit sequences for special meanings, such as the flag sequence, 01111110, for HDLC, SDLC, and ADCCP protocols.

Pertaining to the control of digital equipment in which operations are performed one step at a time at the applicable bit rate.

1. In bit-oriented systems, the transmission of bit strings.
2. In character-oriented systems, the transmission of bit streams that represent characters.
Note: In bit-stream transmission, the bits usually occur at fixed time intervals, start and stop signals are not used, and the bit patterns follow each other in sequence without interruption.

Digital transmission in which two binary pulse trains are combined for transmission over a channel in which the available bandwidth is sufficient for transmission of only one of the two pulse trains at a time if they remain in binary form.

In computer graphics, a representation of an image (which category includes characters) by code or a coding scheme that defines (a) the position of pixels by row (horizontal position) and column (vertical position), and (b) individual pixel characteristics such as gray scale and color. Loosely synonymous with raster.

In computer graphics, an image created with, or represented by, a matrix of pixels. Synonym [loosely] raster graphics.

Abbreviation for Because It's Time NETwork. An early (ca.1981) store-and-forward digital communications network interconnecting universities and research institutions worldwide.
Note: BITNET, which is now obsolete, had a purpose akin to that of the present Internet, but was not nearly so robust, and at a speed of only 9600 b/s, it could not support the data rates presently attainable via the… (Read More →)

Building Integrated Timing Systems

A unit used to express the linear bit density of data in storage.
Note: The abbreviation "bpi" is not in accordance with international standards, and is therefore deprecated.

In a digitized image, the number of bits used to represent the luminance (brightness, gray scale) and chroma (color) information contained in each pixel. Synonym bit depth.

A unit used to express the number of bits passing a designated point per second.
Note 1: For example, for two-condition serial transmission in a single channel in which each significant condition represents a bit, i.e., a 0 or a 1, the bit rate in bits per second and the baud have the same numerical value only if each bit… (Read More →)

Abbreviation for bus interface unit. See network interface device.

1. [A] designation applied to telecommunications and automated information systems, and to associated areas, circuits, components, and equipment, in which only unclassified signals are processed.
Note: Encrypted signals are unclassified. [NIS]
2. Designation applied to information systems, and to associated areas, circuits, components, and equipment, in which national security information is not processed. [INFOSEC-99]

A generic term for a single-purpose device having limited functionality.
Note: A black box is usually represented in schematic drawings as a geometric figure, possibly with defined connector(s), but no details with respect to the type or number of internal components that enable it to perform its defined task.

A composite color video signal comprised of sync, color burst, and black video.
Note: Black burst is used to synchronize (genlock) other video sources to the same sync and color information. Black burst generators are used in video studios to "lock" the entire facility to a common signal ("house sync" or "house black"). [After Silicon]

1. In facsimile systems using amplitude modulation, that form of transmission in which the maximum transmitted power corresponds to the maximum density of the subject.
2. In facsimile systems using frequency modulation, that form of transmission in which the lowest transmitted frequency corresponds to the maximum density of the subject.

Of a television baseband signal (e.g., NTSC composite video), the voltage level corresponding to black or to the maximum limit of black peaks.

Noise that has a frequency spectrum of predominately zero power level over all frequencies except for a few narrow bands or spikes.
Note: An example of black noise in a facsimile transmission system is the spectrum that might be obtained when scanning a black area in which there are a few random white spots. Thus, in the time domain, a… (Read More →)

1. In facsimile systems using amplitude modulation, recording in which the maximum received power corresponds to the maximum density of the record medium.
2. In a facsimile system using frequency modulation, recording in which the lowest received frequency corresponds to the maximum density of the record medium.

In facsimile, the signal resulting from scanning a maximum-density area of the object.

A signal that represents only unclassified or encrypted information, usually in cryptographic systems.

See cipher-text.

A totally absorbing body that does not reflect radiation.
Note: In thermal equilibrium, a blackbody absorbs and radiates at the same rate; the radiation will just equal absorption when thermal equilibrium is maintained.

The interference that is caused by the presence of an AM broadcast signal of one volt per meter (V/m) or greater strengths in the area adjacent to the antenna of the transmitting station. The 1 V/m contour is referred to as the blanket contour and the area within this contour is referred to as the "blanket area. " [47CFR]

In the vicinity of a transmitting antenna, the area in which the signal from that antenna interferes with the reception of other signals.
Note: The blanketing area around a given transmitting antenna depends on the selectivity and sensitivity of the receiver, and on the respective levels of the other signals in question.

1. The period of time in which no video image is displayed. [JP 1-02]
2. In graphic display, the suppression of the display of one or more display elements or display segments.

In raster-scanned television technology, the period between (a) the end of one horizontal scanning line and the beginning of the next (the horizontal blanking interval), or (b) the end of one field and the beginning of the next (the vertical blanking interval), during which the display of picture information is suppressed.
Note 1: Blanking intervals were a necessary part of… (Read More →)

In a baseband television signal, the DC level (nominally 0 volts) from which the amplitudes of the various components of the signal are measured. Conventionally, the viewable parts of the signal (except subcarriers) are positive with respect to blanking, while the synchronizing pulses are negative with respect to blanking. In North American NTSC signals, the darkest portions of the image… (Read More →)

Transmission without obtaining a receipt, i.e., acknowledgement of reception, from the intended receiving station.
Note: Blind transmission may occur or be necessary when security constraints, such as radio silence, are imposed, when technical difficulties with a sender's receiver or receiver's transmitter occur, or when lack of time precludes the delay caused by waiting for receipts.

In graphic display devices, an intentional periodic change in the intensity of one or more display elements or display segments.

1. A group of bits or digits that is transmitted as a unit and that may be encoded for error-control purposes.
2. A string of records, words, or characters, that for technical or logical purposes are treated as a unit.
Note 1: Blocks (a) are separated by interblock gaps, (b) are delimited by an end-of-block signal, and (c) may contain… (Read More →)

See end-of-transmission-block character.

In the processing or transmission of digital data, an error-control procedure that is used to determine whether a block of data is structured according to given rules.

A character added to a transmission block to facilitate error detection.
Note: In longitudinal redundancy checking and cyclic redundancy checking, block check characters are computed for, and added to, each message block transmitted. This block check character is compared with a second block check character computed by the receiver to determine whether the transmission is error free.

An error detection and/or correction code in which the encoded block consists of N symbols, containing K information symbols (K<N) and N-K redundant check symbols, such that most naturally occurring errors can be detected and/or corrected.

A diagram of a system, a computer, or a device in which the principal parts are represented by suitably annotated geometrical figures to show both the basic functions of the parts and their functional relationships.

In the received image in video systems, distortion characterized by the appearance of an underlying block encoding structure.

A process by which one or more of the less significant bits of all the samples stored in a packet are dropped to alleviate congestion. [T1.509-1995]

In a block, the ratio of the number of user information bits to the total number of bits.
Note: For a given block scheme, block efficiency represents the maximum possible efficiency for a given block scheme transmitted over a perfect transmission link.

A block within which at least one bit error occurs when the block is transferred from the source to the destination within the time slot assigned. [After T1.503-1996]

The Service Provider to which a thousands-block (NXX-X) has been assigned for use.

The number of data units, such as bits, bytes, characters, or records, in a block.

The designation of one or more bits in a block as parity bits used to force the block into a selected parity, either odd or even.
Note: Block parity is used to assist in error detection or correction.

The process, initiated by a single action, of transferring one or more blocks of data.

A coordinated sequence of user and telecommunication system activities undertaken to effect transfer of an individual block from a source user to a destination user.
Note: A block transfer attempt begins when the first bit of the block crosses the functional interface between the source user and the telecommunication system. A block transfer attempt ends either in successful block transfer… (Read More →)

The average ratio of user information bits to total bits in successfully transferred blocks.

Failure to deliver a block successfully.
Note: The principal block transfer failure outcomes are: lost block, misdelivered block, and added block.

The number of successful block transfers during a performance measurement period divided by the duration of the period.

The average value of the duration of a successful block transfer attempt.
Note: A block transfer attempt is successful if (a) the transmitted block is delivered to the intended destination user within the maximum allowable performance period and (b) the contents of the delivered block are correct.

The expected block-error ratio.

1. The ratio of the number of incorrectly received blocks to the total number of blocks transferred.
Note: The block-error ratio is calculated using empirical measurements. Multiple block-error ratios may be used to predict block-error probability.
2. The ratio of the number of blocks that contain at least one bit in error to the total number of blocks transmitted in… (Read More →)

The ratio of the number of lost blocks to the total number of block transfer attempts during a specified period.

The ratio of the number of misdelivered blocks to the total number of block transfer attempts during a specified period.

A blocked call is said to have occurred when a call presented to a telecommunications Service Provider (SP) facility cannot be completed due to Blocking.

1. The formatting of data into blocks for purposes of transmission, storage, checking, or other functions.
2. Denying access to, or use of, a facility, system, or component.
3. The failure of a telecommunications network to meet a user service demand, because of the lack of an available communications path.

In telephone traffic engineering, a criterion that specifies the maximum number of calls or service demands that fail to receive immediate service.
Note: The blocking criterion is usually expressed in probabilistic notation, such as P.001.

The number of records in a block.
Note: The blocking factor is calculated by dividing the block length by the length of each record contained in the block. If the records are not of the same length, the average record length may be used to compute the blocking factor. Synonym grouping factor.

A specific probability distribution function intended to model calling patterns of users who fail to find available facilities.
Note: There are several blocking formulas. The applicability of each to a given situation depends on its underlying assumptions regarding caller behavior.

In telecommunications, a network that has fewer transmission paths than would be required if all users were to communicate simultaneously.
Note: Blocking networks are used because not all users require service simultaneously. Certain statistical distributions apply to the patterns of user demand.

In a spectrum of frequencies, a region in which the spectral density, i.e., power per hertz, is proportional to the frequency.

See chroma keying.

A low-power, short-range, rf technology that allows the connection of intelligent communications devices or appliances in a household or an office in a short-range wireless network. Examples of Bluetooth applications are transferring data between cell phones, radios, pagers, personal digital assistants, notebook computers, video and still cameras, audio players, and local area networks.

In television and video systems, a global distortion over the entire image, characterized by reduced sharpness of edges and limited spatial detail. [T1.80
1. 02-1996]

Broadcast/Multicast Control

Broadcast Notification

A type of bayonet (twist-lock) coaxial connector commonly used in applications involving small (e.g., RG-59, RG-62) coaxial cables.

Backus-Naur Form

Abbreviation for Bell Operating Company.

Business Operations Framework

The number that relates the average energy of a molecule to its absolute temperature.
Note: Boltzmann's constant is approximately
1. 38 × 10-23 J/K (joules/kelvin).

Business Operations Map

An electrical connection that provides a low-resistance path between two conducting surfaces.

1. In electrical engineering, the process of connecting together metal parts so that they make low resistance electrical contact for direct current and lower frequency alternating currents. [JP1]
2. The process of establishing the required degree of electrical continuity between two or more conductive surfaces that are to be joined.

A name or address of an Internet resource, stored in a software file at a user's site, e.g., in a desktop computer, for convenient future use.
Note: An example of a bookmark is an entry in a bookmark file (or bookmark list) such as maintained within or by a Web browser for the convenience of the user in revisiting a… (Read More →)

Synonym hotlist.

1. A mathematical function that describes Boolean operations.
2. A switching function in which the number of possible values of the function and each of its independent variables is two.

1. Any operation in which each of the operands and the result take one of two values.
Note: Typical states are "0 or 1," "on or off," "open or closed," or "present or absent. "
2. An operation that follows the rules of Boolean Algebra.

To take some kind of assenting action to initiate computer bootup, e.g., to turn on the primary power (often referred to as initiating a cold bootup) or restart a powered-up computer (often referred to as initiating a hot bootup or hot reboot).

Bootstrap Protocol

1. A technique or device designed to bring about a desired state by means of its own action.
2. That part of a computer program that may be used to establish another version of the computer program.
3. The automatic procedure whereby the basic operating system of a processor is reloaded following a complete shutdown or loss of memory.
4.… (Read More →)

In computer science, the initial sequence of events (usually preprogrammed in firmware present in the computer) that are necessary to start a computer; i.e., to initialize its operating system, load programs into memory, etc. , when (a) it is first powered up, or (b) when already powered up, upon some kind of assenting action by the user.

1. The physical axis of a directional antenna.
2. To align a directional antenna, using either an optical procedure or a fixed target at a known location.

See BCH code.

Baseline Operating Systems Security

Abbreviation for robot. A relatively small and focused computer application that (a) runs continuously, in the background (i.e., simultaneously), as other programs are being run, and (b) responds automatically to a user's activity. Synonyms agent, droid, infobot.
Note 1: Many bots are created for the benefit of the user, e.g., those that send information upon request, perform automated searches, or… (Read More →)

To return, to the sender, e-mail that is, for whatever reason, undeliverable to its intended destination.
Note 1: There are various reasons why e-mail may be bounced. Examples are an incorrect address, problems with local network facilities, and problems with telecommunications links.
Note 2: Bounced e-mail is often accompanied by an error message describing the reason that it was not… (Read More →)

The hour in which the highest usage is measured for any day. The readings are on the hour or half hour. The selected clock hour will vary from day to day, depending on the measured usage. [T
1. Rpt 11-1991]

In an optical fiber, a mode that (a) has a field intensity that decays monotonically in the transverse direction everywhere external to the core and (b) does not lose power to radiation.
Note: Except for single-mode fibers, the power in bound modes is predominantly contained in the core of the fiber. [After 2196] Synonymstrapped mode.

Synonym guided ray.

1. [In security,] Software, hardware, or a physical barrier that limits access to a system or part of a system. [INFOSEC-99]
2. Synonym [in networking]section boundary.

Business Process Execution Language

See bits per inch.

Broadband Power Line

Business Process Management

Business Process Modeling Notation

Broadband Passive Optical Network

bits per second

1. An essential part of many fiber-optic cable designs, consisting of a layer of woven yarn.
Note: In the case of single-fiber loose-buffered or two-fiber "zip-cord" loose-buffered fiber-optic cables, the braid is situated between the buffer tube and jacket. In the case of cables having multiple buffer tubes, the braid is usually situated between the inner jacket and outer jacket.… (Read More →)

1. In a computer program, a conditional jump or departure from the implicit or declared order in which instructions are being executed.
2. To select a branch, as in definition ,
1.
3. A direct path joining two nodes of a network or graph.
4. In a power distribution system, a circuit from a distribution device (power panel) of a… (Read More →)

A network point where two or more possible routes through different intermediate networks from the origination network to destination network physically diverge. A branch point may occur in any network except the destination network. [T1.118-1992]

A network used for transmission or reception of signals over two or more channels.

A repeater with two or more outputs for each input.

The circumvention or disablement of some element of computer security, with or without detection, which could result in a penetration of (a) the affected computer's software or data base(s), or (b) another device or network to which the affected computer may also be connected. [After 2382-pt.8]

1. An assembly of circuits or parts used to prove the feasibility of a device, circuit, system, or principle with little or no regard to the final configuration or packaging of the parts.
2. To prepare a breadboard.

1. In dial-pulse signaling, that portion of the dial pulse in which the pulsing circuit is in its high-impedance condition. [T1.405-1989]
2. In dial-pulse signaling, that portion of the dial pulse in which the pulsing circuit is on-hook. [T1.409-1996]

To separate the individual fibers or buffer tubes of a fiber-optic cable for the purpose of splicing or installing optical connectors. [After FAA] Synonyms: fan out, furcate.

A testing device that permits a user to access individual leads of an interface cable, using jumper wires, in order to monitor, switch, or patch the electrical output of the cable.

A multifiber fiber-optic cable design in which individual fibers, usually tight-buffered, are surrounded by separate strength members and jackets, which are in turn enveloped by a common jacket.
Note 1: The breakout cable facilitates easy installation of fiber-optic connectors. All that need be done to prepare the ends of the cable to receive connectors is to remove the outer jacket,… (Read More →)

A kit of materials, composed of an outer jacket in which is contained a strength member consisting of a bundle of usually aramid yarn, which jacket and yarn may be slipped over a loose buffer tube containing a single fiber, to convert the buffer tube and fiber to a complete single-fiber cable to which a fiber-optic connector may be directly… (Read More →)

For a plane electromagnetic wavefront incident on a plane boundary between two dielectric media having different refractive indices, the angle of incidence at which transmittance from one medium to the other is unity when the wavefront is linearly polarized with its electric vector parallel to the plane of incidence.
Note 1: Brewster's angle _B, is given by where n₁ and… (Read More →)

See Brewster's angle.

Abbreviation for basic rate interface.

An informal name for a hand-held radiotelephone unit. Synonymsradio personal terminal.

A low-pass filter with a steep cut-off (such as 20 dB/octave or greater), such that a negligible amount of higher frequency information passes.
Note: A brick wall filter typically has uniform group delay. [After SMPTE]

1. In communications networks, a device that (a) links or routes signals from one ring or bus to another or from one network to another, (b) may extend the distance span and capacity of a single LAN system, (c) performs no modification to packets or messages, (d) operates at the data-link layer of the OSI--Reference Model (Layer 2), (e) reads… (Read More →)

A device that electrically or physically removes bridged telephone pairs.
Note: Relays, saturable inductors, and semiconductors are used as bridge lifters.

Synonym hybrid coil.

A ship station operating in the port operations service in which messages are restricted to navigational communications and which is capable of operation from the ship's navigational bridge or, in the case of a dredge, from its main control station, operating on a frequency or frequencies in the 156-162 MHz band. [NTIA]

The part of a signaling system in which ringers associated with a particular line are connected across that line.

Any portion of a loop that is not in the direct talking path between the central office and the service user's terminating equipment. A bridged tap may be an unused cable pair connected at an intermediate point or an extension of the circuit beyond the service user's location.
Note: A bridged tap creates an impedance mismatch within the transmission line,… (Read More →)

A parallel connection used to extract some of the signal energy from a circuit, usually with negligible effect on the normal operation of the circuit.

At a given frequency, the loss that results when an impedance is connected across a transmission line.
Note: Bridging loss is expressed as the ratio, in dB, of the signal power delivered, prior to bridging, to a given point in a system downstream from the bridging point, to the signal power delivered to the given point after bridging.

An attribute of visual perception in which a source appears to emit a given amount of light.
Note 1: "Brightness" should be used only for nonquantitative references to physiological sensations and perceptions of light.
Note 2: "Brightness" was formerly used as a synonym for the photometric term "luminance" and (incorrectly) for the radiometric term "radiance. "

See Brillouin scattering.

In a physical medium, scattering of lightwaves, caused by thermally driven density fluctuations.
Note: Brillouin scattering may cause frequency shifts of several gigahertz at room temperature. [From Weik '89]

1. Synonym [in analog technology] wideband.
2. A descriptive term for evolving digital technologies that provide consumers a signal-switched facility offering integrated access to voice, high-speed data service, video-demand services, and interactive delivery services. [FCC]

A communications switch capable of interconnecting channels having bandwidths greater than voice bandwidth.

An Integrated Services Digital Network (ISDN) offering broadband capabilities.
Note 1: B-ISDN is an ITU-T proposed (originally a CCITT-proposed) service that may (a) include interfaces operating at data rates from 150 to 600 Mb/s, (b) use asynchronous transfer mode (ATM) to carry all services over a single, integrated, high-speed packet-switched network, (c) have LAN interconnection capability, (d) provide access to… (Read More →)

See [in analog technology] wideband.

The transmission of signals that may be simultaneously received by stations that usually make no acknowledgement.

A space station in the broadcasting-satellite service (sound broadcasting). [NTIA]

A radiocommunication service in which the transmissions are intended for direct reception by the general public. This service may include sound transmissions, television transmissions or other types of transmissions. [NTIA] [RR]

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

A radiocommunication service in which signals transmitted or retransmitted by space stations are intended for direct reception by the general public. In the broadcasting-satellite service, the term "direct reception" shall encompass both individual reception and community reception. [NTIA] [RR]

Synonym billboard antenna.

A combined bridge and router that operates without protocol restrictions, routes data using a protocol it supports, and bridges data it cannot route.

Any computer software program for reading hypertext.
Note 1: Browsers are usually associated with the Internet and the World Wide Web (WWW).
Note 2: A browser may be able to access information in many formats, and through different services including HTTP and FTP.

[The] act of searching through information-system (IS) storage to locate or acquire information without necessarily knowing of the existence or the format of the information being sought. [INFOSEC-99]

In security, an attack that requires trying all (or a large fraction of all) possible values until the right value is found. Synonym [loosely] exhaustive attack.

Base Station.

Abbreviation for basic serving arrangement.

Abbreviation for basic service element.

Abbreviation for British Standards Institution.

Business Support System

Base Station Switching System

Base Transceiver Station

Synonym proration.

1. A routine or storage medium used to compensate for a difference in rate of flow of data, or time of occurrence of events, when transferring data from one device to another.
Note: Buffers are used for many purposes, such as (a) interconnecting two digital circuits operating at different rates, (b) holding data for use at a later time, (c)… (Read More →)

Synonym buffer.

Common coding style is to never allocate large enough buffers, and to not check for overflows. When such buffers overflow, the executing program (daemon or set-uid program) can be tricked in doing some other things. Generally this works by overwriting a function's return address on the stack to point to another location.

1. A concealed microphone or listening device or other audiosurveillance device. [JP 1-02]
2. A mistake in a computer program.
3. To install means for audiosurveillance. [JP 1-02]
4. A semiautomatic telegraph key.
5. A mistake or malfunction.

The maximum variable transmission and processing delay that is permitted in a wideband network. Each PVP (packetized voice protocol) node records the delay that it adds and updates accordingly the TS (time stamp) value in the packet header. When the terminating endpoint of a PVP node receives a voice packet, the provisioned build-out and the time stamp value are compared.… (Read More →)

The process of adding a combination of inductance, capacitance, and resistance to a cable pair so that its electrical length may be increased by a desired amount to control impedance and loss characteristics. Synonym line buildout.

Simultaneous encryption of all channels of a multichannel telecommunications link. [INFOSEC]
Note: A single encryption device can be used to encrypt the output signal from a multiplexer.

A form of electronic messaging in which addressed messages or files are entered by users into a computer or network of computers.
Note: Other users may obtain, at their convenience and request, messages or files available to them. Synonymelectronic bulletin board.

A frame-alignment signal in which the signal elements occupy consecutive digit positions.

1. A group of optical fibers or electrical conductors, such as wires and coaxial cables, usually in a single jacket.
Note: Multiple bundles of optical fibers or electrical conductors may be placed in the same cable. [After 2196]
2. In cryptography, the three cryptographic keys (K1, K2, K3) used with a TDEA mode. [After X9.52] [After X9.65]

See direct-buried cable.

See direct-buried cable.

1. In data communications, a sequence of signals, noise, or interference counted as a unit in accordance with some specific criterion or measure.
2. To separate continuous-form or multipart paper into discrete sheets.

Deprecated synonym for isochronous burst transmission.

In a packet-switched network, a switching capability in which each network switch extracts routing instructions from an incoming packet header to establish and maintain the appropriate switch connection for the duration of the packet, following which the connection is automatically released.
Note: In concept, burst switching is similar to connectionless mode transmission, but it differs from the latter in that… (Read More →)

1. Transmission that combines a very high data signaling rate with very short transmission times.
2. Operation of a data network in which data transmission is interrupted at intervals.
Note: Burst transmission enables communications between data terminal equipment (DTEs) and a data network operating at dissimilar data signaling rates. Synonym data burst.

One or more conductors or optical fibers that serve as a common connection for a group of related devices.

See network interface device.

See network topology.

See network topology.

The iconectiv® Business Integrated Routing and Rating Database System is a centrally maintained database into which Service Providers (SP) or their agents enter data that supports the routing and rating of calls. Data reflects all North American Numbering Plan (NANP) (CEntral Office (CO) Code (NPA-NXX) and Thousands-Block (NPA-NXX-X) assignments and is closely aligned with many of the processes and data… (Read More →)

Deprecated term. See busy signal.

In a communications system, the sliding 60-minute period during which occurs the maximum total traffic load in a given 24-hour period.
Note 1: The busy hour is determined by fitting a horizontal line segment equivalent to one hour under the traffic load curve about the peak load point.
Note 2: If the service time interval is less than 60 minutes,… (Read More →)

During a 1-year cycle, the period of 3 consecutive months having the highest busy hour traffic.

1. In telephony, an audible or visual signal that indicates that no transmission path to the called number is available. Synonym busy tone.
2. In telephony, an audible or visual signal that indicates that the called number is occupied or otherwise unavailable. Synonym reorder tone.

In telephony, a test made to determine whether certain facilities, such as a subscriber line or a central office trunk, are available for use.

Synonym busy signal.

In a public switched telephone network, a network-provided service feature that permits an attendant to verify the busy or idle state of station lines and to break into the conversation.
Note: A 440-Hz tone is applied to the line for 2 seconds, followed by a
0. 5-second burst every 10 seconds, to alert both parties that the attendant is connected… (Read More →)

Abbreviation for bandwidth.

1. The use of any telecommunications facilities or services that circumvents those of the local exchange common carrier.
Note: Bypass facilities or services may be either customer-provided or vendor-supplied.
2. An alternate circuit that is routed around equipment or system component.
Note: Bypasses are often used to allow system operation to continue when the bypassed equipment or a system component… (Read More →)

A sequence of contiguous bits (usually 8) considered as a unit.
Note: In pre-1970 literature, "byte" referred to a variable-length bit string. Since that time, the usage has changed so that now it almost always refers to an 8-bit string. This usage predominates in computer and data transmission literature; when so used, the term is synonymous with "octet. "

1. Loosely, the group of microwave frequencies from 4 GHz to 6 GHz used in satellite communications.
2. The band of satellite downlink frequencies between
3. 7 and
4. 2 GHz.
Note 1: For federal procurement purposes, the radio frequency band(s) must be specified using the upper and lower limits of the band, per 47 CFR
30
0.
Note 2:… (Read More →)

Abbreviation for communications-electronics.

A general-purpose, high-level, structured computer programming language.
Note: C-language was originally designed for and implemented on the UNIXTM operating system.

The term "C-Message Noise" denotes the frequency weighted average noise within an idle voice channel. The frequency weighting, called C-message, is used to simulate the frequency characteristic of the 5OO-type telephone set and the hearing of the average subscriber.

A noise spectral weighting used in a noise power measuring set to measure noise power on a line that is terminated by a 500-type set or similar instrument.
Note: The instrument is calibrated in dBrnC.

The term "C-Notched Noise" denotes the C-message frequency weighted noise on a voice channel with a holding tone, which is removed at the measuring end through a notch (very narrow band) filter.

Abbreviation for central office.

Abbreviation for carrier-to-receiver noise density.

Carrier to Noise Density Ratio

Abbreviation for command and control warfare.

Carrier Aggregation

1. An assembly of one or more insulated conductors, or optical fibers, or a combination of both, within an enveloping jacket.
Note 1: A cable is constructed so that the conductors or fibers may be used singly or in groups.
Note 2: Certain types of communications cables, especially long submarine cables but also terrestrial cables, whether the communications media are… (Read More →)

A cable that is ready for installation in specific applications and usually terminated with connectors.

For a cabled single-mode optical fiber under specified length, bend, and deployment conditions, the wavelength at which the fiber's second order mode is attenuated a measurable amount when compared to a multimode reference fiber or to a tightly bent single-mode fiber.

The ratio of cable conductor or cable pair kilometers in use to total cable conductor or cable pair kilometers available in the plant, e.g., the ratio of revenue producing cable pair kilometers in use to total cable pair kilometers in plant. [47 CFR Pt.36-A]

Synonym [in cable television] headend.

See sheath.

In CATV systems, a bidirectional high-speed digital communications interface, located on a subscriber's or user's premises, and used, for example, for Internet access or other digital communications.

A fixed or mobile station used for the transmission of television and related audio signals, signals of standard and FM broadcast stations, signals of instructional television fixed stations, and cablecasting from the point of reception to a terminal point from which the signals are distributed to the public. [47CFR]

A broadband communications technology in which multiple television channels, as well as audio and data signals, may be transmitted either one way or bidirectionally through an often hybrid (fiber and coaxial) distribution system to a single or to multiple specific locations. CATV originated in areas where good reception of direct broadcast TV was not possible. Now CATV also consists of… (Read More →)

1. Carrier Access Code,
2. Customer Administration Center,
3. Connection Admission Control

A buffer, smaller and faster than main storage, used to hold a copy of instructions and data in main storage that are likely to be needed next by the processor and that have been obtained automatically from main storage.

Abbreviation for computer-aided design.

Communications Assistance for Law Enforcement Act

1. In communications, any demand to set up a connection.
2. A unit of traffic measurement.
3. The actions performed by a call originator.
4. The operations required to establish, maintain, and release a connection.
5. To use a connection between two stations.
6. The action of bringing a computer program, a routine, or a subroutine into effect, usually by… (Read More →)

See abandoned call.

The mechanism that allows a user to be alerted on one terminal and to choose to answer the call on any terminal, not necessarily the one through which alerting took place. [T
1. Rpt34-1994]

A call control signal sent by the called terminal to indicate that it accepts the incoming call.

The Call Agent provides call processing, call control, feature control and Operations Administration Maintenance & Provisioning to manage services for a packet network comprised of multiple types of media gateway endpoints. The network itself may transport traffic over many types of packet switching fabric, such as IP, Ethernet, ATM or Frame Relay. The Media Gateways (i.e., Access and Trunk Gateways)… (Read More →)

Signaling required for supervision of a bearer service between two end points, including support for the functions of call origination, call delivery, and handover.

In a telecommunications system, a demand by a user for a connection to another user.
Note: In telephone traffic analysis, call attempts are counted during a specific time frame. The call-attempt count includes all completed, overflowed, abandoned, and lost calls.

[The] procedure for identifying and authenticating a remote information-systems (IS) terminal, whereby the host system disconnects the terminal and reestablishes contact. [INFOSEC-99] Synonym dial back.

1. The contention that occurs when a terminal and data circuit-terminating equipment (DCE) specify the same channel at the same time to transfer a call request and handle an incoming call.
Note: When call collision occurs, the DCE proceeds with the call request and cancels the incoming call.
2. The condition that occurs when a trunk or channel is seized… (Read More →)

The ratio of successfully completed calls to the total number of attempted calls.
Note: This ratio is typically expressed as either a percentage or a decimal fraction.

One of a set of control characters used in call-control signaling.
Note: The signals representing call control characters may be used under defined conditions on interchange circuits other than the originating circuit.

The network intelligence that provides call/connection processing and control. [T1.667-1999]

A member of the set of network management signals used to establish, maintain, or release a call.

The logical link between the device performing an electronic surveillance access function and the LEA (law enforcement agency) that primarily carries call-identifying information. [T1.260-1998]

1. The delay that occurs when a call arrives at an automatic switching device and no channel or facility is immediately available to process the call.
2. The time between the instant a system receives a call attempt and the instant of initiation of ringing at the call receiver end instrument.

A service feature in which call data on a specific telephone extension or group of subscribers are collected and recorded for cost-of-service accounting purposes.

1. The time between (a) the instant a connection, i.e., off-hook condition at each end, is established between the call originator and the call receiver and (b) the instant the call originator or the call receiver terminates the call.
2. In data transmission, the duration of the information transfer phase of an information transfer transaction.

A service feature, available in some switching systems, whereby calls can be rerouted automatically from one line, i.e., station number, to another or to an attendant.
Note: Call forwarding may be implemented in many forms.

CG is a code control that regulates the maximum rate at which calls are released toward a destination code. Equipment vendors commonly provide the capability to Call Gap at intervals of
0. 10 to 600 seconds on a range of numbers from three (3), six (6), or seven (7), through ten (10) digits.

A service feature in which a user may retain an existing call while accepting or originating another call using the same end instrument.

A network utility that consists of a name assigned by the originating network for each established or partially established virtual call.
Note: When a call identifier is used in conjunction with the calling data terminal equipment (DTE) address, the call identifier uniquely identifies the virtual call.

Synonym traffic intensity.

1. In telegraphy, route selection, signaling, and circuit usage and availability for a call.
2. In universal personal telecommunications, the ability of a user to inform the network how to handle incoming calls in accord with certain parameters, such as the call originator, the time of day, and the nature of the call.
Note: Call management is accomplished by means… (Read More →)

An entity, such as a person, equipment, or program that originates a call. Synonym calling party.

A service feature of some switching systems enabling a user, by dialing a predetermined code, to answer incoming calls that are directed to another user in a preselected call group.