Synonym normalized frequency.

The interface point in an ISDN environment between the line termination and the exchange termination.

Sets of telecommunications protocols and interfaces defined by CCITT (now ITU-T) Recommendations.
Note: Some of the more common V. -series Recommendations are:V.21: A CCITT Recommendation for modem communications over standard commercially available lines at 300 b/s. This protocol is generally not used in the United States.
V.22bis: A CCITT Recommendation for modem communications over standard commercially available voice-grade channels at… (Read More →)

Vehicle to Vehicle

Vehicle to Everything

A call-disposition category for a call attempt to an unassigned NPA (numbering plan area) or N. [T1.207-1998]

This announcement is played when a customer mis-dialed or the NPA-NXX or NXX-X is not valid. An example of such a recording is as follows: “We’re sorry, your call cannot be completed as dialed. Please, check the number and try again. ” (See “NIIF Reference Document Part 2 – Installation and Maintenance Responsibilities for SS7 Links and Trunks Attachment H… (Read More →)

Synonym anti-virus program.

1. Tests to determine whether an implemented system fulfills its requirements.
2. The checking of data for correctness or for compliance with applicable standards, rules, and conventions.
3. [The] process of applying specialized security test and evaluation procedures, tools, and equipment needed to establish acceptance for joint usage of an information system (IS) by one or more departments or agencies… (Read More →)

The system containing the data base information to be used in validation of the telecommunications charge card or billed number screening data.

The date the transfer entry to an account is considered effective; either the day the instruction is received or some future date as stipulated by the originator. [After X9.9]

A company that sells the services of a value-added network.

A network using the communication services of other commercial carriers, using hardware and software that permit enhanced telecommunication services to be offered.

Acronym for value-added network.

Volt-ampere reactive.

A buffer into which data may be entered at one rate and removed at another rate without changing the data sequence.
Note: Most first-in first-out (FIFO) storage devices are variable-length buffers in that the input rate may be variable while the output rate is constant or the output rate may be variable while the input rate is constant. Various clocking… (Read More →)

See continuously variable slope delta modulation.

In statistics, in a population of samples, the mean of the squares of the differences between the respective samples and their mean, expressed mathematically as: where n is the number of samples, xi is the value of sample i, is the mean of the samples, and 2 is the variance.
Note: The square root of the variance, , is the… (Read More →)

1. One of two or more code symbols having the same plain text equivalent. [INFOSEC-99]
2. One of several plain text meanings that are represented by a single code group. [JP1]

A new key formed by a nonsecret process with the original key, such that one or more of the nonparity bits of the new key differ from the corresponding bits of the original key. [After X9.8]

In ac power distribution, a device for sensing deviations of any measured variable, such as voltage, current, or frequency, and capable of initiating a programmed action, such as transfer to other power sources, when programmed limits of voltage, current, frequency, or time are exceeded, or providing an alarm, or both.

Variable Bit Rate

1. virtual circuit,
2. vacant code,
3. virtual channel,
4. virtual concatenation.

1. virtual channel connection,
2. voice call continuity.

Abbreviation for video cassette recorder. See video recorder.

Very high bit-rate Digital Subscriber Line

Very high bit-rate Digital Subscriber Line/2

Abbreviation for visual display unit. See monitor.

Synonym array processor.

Of an electrical or electromagnetic signal, its speed in a physical medium such as a coaxial cable or optical fiber.

1. In information assurance, comparing an activity, a process, or a product with the corresponding requirements or specifications.
Note: Examples of verification are comparing a specification with a security policy model or comparing object code with source code. [2382-pt.8]
2. [The] process of comparing two levels of an information system (IS) specification for proper correspondence (e.g., security policy model with… (Read More →)

Information used by a verifier to verify an identity claimed through exchange AI [10181-2].

Development of a system or part of a system where the transformation from one representation to another is mathematically proven, or demonstrated to be consistent by an argument of equivalent value [CESG].

In telephone systems, a service provided by a unit that is inserted on each end of a transmission circuit for the purpose of verifying supervisory signals on the circuit. See automatic ringdown circuit.

1. The entity that verifies the authenticity of a digital signature. [After X9.31]
2. An entity which is or represents the entity requiring an authenticated identity. A verifier includes the functions necessary for engaging in authentication exchanges [10181-2].

An extremely secure cryptographic approach to enciphering messages, wherein each character of a message gets assigned a random character from the key; the one-time keypad is physically delivered to the receiver and then is destroyed.
Note: The Vernam cypher requires the prospective user to first courier the megabyte key to the intended message partner. The Vernam cypher is the only… (Read More →)

There is a version element associated with each Virtual Channel Description, Virtual Channel Map, and Master SI table. A version is changed when any element, attribute, or linked file is modified. Since it expected that the System Information is stable once a network has been established, this allows for the ITF Device to monitor only one file, the Master SI… (Read More →)

In an optical fiber, the angle formed by the extreme bound meridional rays accepted by the fiber, or emerging from it, equal to twice the acceptance angle; the angle formed by the largest cone of light accepted by the fiber or emitted from it. [FAA]

A Web search engine that locates very precisely a few Web pages of particular interest according to the character strings or subject entered as the search topic.

Synonym transverse redundancy check.

Frequencies from 30 MHz to 300 MHz. See electromagnetic spectrum.

Frequencies from 3 kHz to 30 kHz. See electromagnetic spectrum.

Modified AM transmission in which one sideband, the carrier, and only a portion of the other sideband are transmitted.

Abbreviation for voice frequency.

See voice frequency primary patch bay.

Abbreviation for voice frequency carrier telegraph. See voice-frequency telegraph.

Abbreviation for voice-frequency carrier telegraph. See voice-frequency telegraph.

Abbreviation for voice-frequency telegraph.

Abbreviation for very high frequency. See electromagnetic spectrum.

Pertaining to circuit performance prediction and description that allows circuit parameters to be predetermined and the circuit to be designed to meet established criteria by analyzing actual, theoretical, and calculated losses.

1. An electrical signal containing timing (synchronization), luminance (intensity), and often chrominance (color) information that, when displayed on an appropriate device, gives a visual image or representation of the original image sequences.
Note: Correlated audio is included and usually implied.
2. Pertaining to the sections of a television system that carry television signals, either in unmodulated or modulated form.
3.… (Read More →)

See codec.

An audio narration for television viewers who are blind or visually disabled, which consists of verbal descriptions of key visual elements in a television program, such as settings and actions not reflected in dialog. [FCC]
Note: Narrations are usually inserted into the program's naturally occurring pauses, and are typically provided through the secondary audio programming channel. [After FCC]

Synonym visual display unit. See monitor.

Synonym visual display terminal. See monitor.

See frame.

A sequence of video frames. [T1.80
1. 02-1996]

Refers, in the context of this document, to all forms of on-demand content that are streamed at the request of a subscriber. This can include, for example, movies, music, radio talk shows, distance learning, games, etc.

Transmission cable containing low-loss pairs with an impedance of 125 ohms; used for telephone carrier circuits, closed-circuit TV, TV pick-ups etc.

Equipment for recording the video waveform so that the mapped images may be stored and later retrieved as the video waveform. [After SMPTE]

A server that distributes video images on demand. [2382-pt.35]

The standard video-signal waveform, measured in IRE units. [After T
1. Rpt16-1992]

1. A teleconference that includes video communications.
2. Pertaining to a two-way electronic communications system that permits two or more persons in different locations to engage in the equivalent of face-to-face audio and video communications.
Note: Video teleconferences may be conducted as if all of the participants were in the same room.

Equipment that performs video teleconference functions, such as coding and decoding of audio and video signals and multiplexing of video, audio, data, and control signals, and that usually does not include I/O devices, cryptographic devices, network interface equipment, network connections, or the communications network to which the unit is connected.

See video teleconference.

1. A telephone that is coupled to an imaging device that enables the call receiver or the call originator, or both, to view one another as on television, if they so desire. [From Weik '89]
2. A military communications terminal that (a) has video teleconference capability, (b) is usually configured as a small desktop unit, designed for one operator, and… (Read More →)

In satellite communications, the quality or degree of visibility of a satellite to a ground station; i.e., the degree to which the satellite is sufficiently above the horizon and clear of obstructions so that it is within a clear line of sight by an Earth terminal.
Note: A pair of satellite Earth terminals has a satellite in mutual view when… (Read More →)

A type of information-retrieval service in which a subscriber can (a) access a remote database via a common carrier channel, (b) request data, and (c) receive requested data on a video display over a separate channel.
Note: The access, request, and reception are usually via common carrier broadcast channels.

Application software that enables a user to have read-only access to electronic documents or images. [After 2382-pt.35]

See AMI violation.

A call, established over a network, that uses the capabilities of either a real or virtual circuit by sharing all or any part of the resources of the circuit for the duration of the call.

A service feature in which (a) a call set-up procedure and a call disengagement procedure determine the period of communication between two data terminal equipments (DTEs) in which user data are transferred by the network in the packet mode of operation, (b) end-to-end transfer control of packets within the network is required, (c) data may be delivered to the network… (Read More →)

Synonym virtual call capability.

In radio or carrier systems in which no carrier is transmitted, e.g., single sideband or double sideband with suppressed carrier, the location in the frequency spectrum that the carrier would occupy if it were present.

The communication channel associated with a virtual channel connection (VCC) that provides for the transport of asynchronous transfer mode (ATM) cells among ATM active elements. A VCC is an association established at the ATM Layer between two or more endpoints for the purpose of user-user, user-network, or network-network information transfer. A VCC consists of the concatenation of virtual channel links… (Read More →)

A concatenation of VCLs (virtual channel links) that extends between the points where the ATM (asynchronous transfer mode) service users access the ATM Layer. The points at which the ATM cell payload is passed to, or received from, the user of the ATM Layer (i.e., a higher layer or ATM management entity) for processing, signifying the endpoints of a VCC.… (Read More →)

Contains the parameters necessary to acquire and display particular AV content. A Virtual Channel Description is made up of one or more Programming Sources. In addition, where possible, a priori knowledge is given of certain parameters required to receive and decode the virtual channel. This may include video and audio codecs.

A means of unidirectional transport of ATM cells between the point where a VCI value is assigned and the point where that value is translated or removed. [T1.630-1999]

A list of virtual channels, containing for each virtual channel a service identifier and a pointer to service description information for the virtual channel. A Virtual Channel Map consists of multiple Virtual Channel Descriptions.

A television service in which a continuous stream flows in real time from the service provider to the terminal device and where the user cannot control the temporal order in which contents are delivered. Also known as a Linear TV Service.

A communications arrangement in which data from a source user may be passed to a destination user over various real circuit configurations during a single period of communication.
Note: Virtual circuits are generally set up on a per-call basis and are disconnected when the call is terminated; however, a permanent virtual circuit can be established as an option to provide… (Read More →)

A network-provided service feature in which a user is provided with a virtual circuit.
Note: Virtual circuit capability is not necessarily limited to packet mode transmission. For example, an analog signal may be converted to a digital signal and then be routed over the network via any available route.

A logical connection that is made to a virtual circuit.

A wideband protocol that is used to transport digital data packets arriving from the channelized side in HDLC frames. [T1.509-1995]

An alias for an IP address or server operated by an Internet Presence Provider or an Internet Service Provider. The virtual domain allows individuals or companies to have a domain name without the effort and cost of maintaining a server. [Bahorsky]

The apparent height of an ionized layer, as determined from the time interval between the transmitted signal and the ionospheric echo at vertical incidence.

Synonym teletraining.

A computer network using internetworks as data links that are transparent for users and that do not have restrictions on protocols, so that the network has the characteristics of a local area network.
Note: Data links over internetworks often use tunneling. [2382-pt.35]

In computer systems, the memory as it appears to, i.e., as it is available to, the operating programs running in the central processing unit (CPU).
Note: The virtual memory may be smaller, equal to, or larger than the real memory present in the system.

A network that provides virtual circuits and that is established by using the facilities of a real network.

A work environment in which employees work cooperatively from different locations using a computer network. [After 2382-pt.35] Synonym virtual workplace.

[An] information system (IS) password computed from a passphrase meeting the requirements of password storage (e.g., 64 bits). [INFOSEC-99]

See virtual circuit.

[A] protected information-system (IS) link utilizing tunneling, security controls (see information assurance), and end-point address translation giving the user the impression a dedicated line exists between nodes. [INFOSEC-99]

An interactive, computer-generated simulated environment with which users can interact using specialized peripherals such as data gloves and head-mounted computer-graphic displays.

The storage space that may be regarded as addressable main storage by the user of a computer system in which virtual addresses are mapped into real addresses.
Note: The size of virtual storage is limited by the addressing scheme of the computer system and by the amount of auxiliary storage available, and not by the actual number of main storage… (Read More →)

In open systems, an application service that (a) allows host terminals on a multi-user network to interact with other hosts regardless of terminal type and characteristics, (b) allows remote log-on by local-area-network managers for the purpose of management, (c) allows users to access information from another host processor for transaction processing, and (d) serves as a backup facility.

A structure designed for transport and switching of sub-STS-1 payloads. There are currently four sizes of VT. [T1.105-1988]

Synonym virtual office.

A simulated environment that appears to have the characteristics of some other environment, and in which participants perceive themselves as interactive parts.

1. An unwanted program which places itself into other programs, which are shared among computer systems, and replicates itself.
Note: A virus is usually manifested by a destructive or disruptive effect on the executable program that it affects.
2. Self-replicating, malicious program segment that attaches itself to an application program or other executable system component and leaves no obvious signs… (Read More →)

A unique bit string that is common to each copy of a particular virus and that may be used by a scanning program to detect the presence of the virus. [2382-pt.8]

The region of the electromagnetic spectrum that can be perceived by human vision, approximately the wavelength range of
0. 4 m to
0. 7 m.

A means for delivering video frames from one point to another; a sequence of frames submitted to the channel input results in a similar (not necessarily identical) sequence of frames at the channel output.
Note: The visual channel may be comprised of the following components: video format conversion devices, encoders (compressors) and decoders (decompressors), rate smoothing buffers, multiplexors and demultiplexors,… (Read More →)

See monitor.

A group of audiovisual services including videophone as defined in ITU-T Recommendation F.721 and videoconferencing (defined in ITU-T H-Series Recommendations). [T1.80
0. 01-1995]

Glass consisting of almost pure silicon dioxide (SiO2). Synonym fused silica.

Virtual Local Area Network

Abbreviation for very low frequency. See electromagnetic spectrum.

Visitors Location Register

Abbreviation for via net loss.

Abbreviation for voice-coder. A device that usually consists of a speech analyzer, which converts analog speech waveforms into narrowband digital signals, and a speech synthesizer, which converts the digital signals into artificial speech sounds.
Note 1: For COMSEC purposes, a vocoder may be used in conjunction with a key generator and a modulator-demodulator to transmit digitally encrypted speech signals over… (Read More →)

Video on Demand

Acronym for voice-operated device anti-sing. A device used to prevent overall voice-frequency singing in a two-way telephone circuit by ensuring that transmission can occur in only one direction at any given instant.

Acronym for voice-operated gain-adjusting device. A device that has a substantially constant output amplitude over a wide range of input amplitudes.

Synonym voice frequency.

See vocoder.

A UIH (unnumbered information with header check) frame that contains a voice packet in its information field. [T1.312-1991]

Pertaining to those frequencies within that part of the audio range that is used for the transmission of speech.
Note 1: In telephony, the usable voice-frequency band ranges from approximately 300 Hz to 3400 Hz.
Note 2: In telephony, the bandwidth allocated for a single voice-frequency transmission channel is usually 4 kHz, including guard bands. Synonym voice band. See electromagnetic… (Read More →)

A patching facility that provides the first appearance of local-user VF circuits in the technical control facility (TCF).
Note: The VF primary patch bay provides patching, monitoring, and testing for all VF circuits. Signals will have various levels and signaling schemes depending on the user terminal equipment.

Synonym voice-frequency telegraph.

In the public regulated telecommunications services, a service grade that is described in part 68, Title 47 of the Code of Federal Regulations [CFR].
Note: Voice-grade service does not imply any specific signaling or supervisory scheme.

The field within a voice packet that contains blocks arranged according to the significance of the bits: the first block contains the most significant bits (MSBs) of all samples, the second contains the second MSBs, and so on. Within a block, bits are ordered according to their corresponding sample numbers. [After T1.312-1991]

Synonym vox.

Synonym vox.

The element that provides routing information to support the routing of VoIP emergency calls, and cooperates in delivering location information to the PSAP over the existing ALI DB infrastructure. The VPC supports access to the routing data in the Emergency Routing Database.

See quasi-analog signal.

A channel capable of carrying analog and quasi-analog signals.

A method of multiplexing one or more dc telegraph channels onto a nominal 4-kHz voice frequency channel. Synonym voice frequency carrier telegraph.

See vodas.

See vogad.

Synonym composited circuit.

Voice over Internet Protocol

The VPC is a NENA i2 functional element that provides routing information based on location of VoIP emergency calls. It also delivers location information to the PSAP over the existing ALI DB infrastructure.

The VPC is a NENA i2 functional element that provides routing information based on location of VoIP emergency calls. It also delivers location information to the PSAP over the existing ALI DB infrastructure.

A storage device in which the contents are lost when power is removed.

See data volatility.

In alternating-current power transmission and distribution, the product of the rms voltage and amperage, i.e., the apparent power, multiplied by the sine of the phase angle between the voltage and the current.
Note 1: Vars represents the power not consumed by a reactive load, i.e., when there is a phase difference between the applied voltage and the current.
Note 2:… (Read More →)

The highest voltage that can be applied to a wire or conductor in conformance with standards.

In a transmission line, the ratio of maximum to minimum voltage in a standing wave pattern.
Note: The VSWR is a measure of impedance mismatch between the transmission line and its load. The higher the VSWR, the greater the mismatch. The minimum VSWR, i.e., that which corresponds to a perfect impedance match, is unity.

A portion of data, with its physical storage medium, that can be handled conveniently as a unit.
Note: An example of a volume is a "floppy" diskette.

A unit of measurement of the power of an audio-frequency signal, as measured by a vu meter.
Note 1: The vu meter is built and used in accordance with American National Standard C16.5-194
2.
Note 2: When using the vu meter to measure sine wave test tone power, 0 vu equals 0 dBm.

An acoustoelectric transducer and a keying relay connected so that the keying relay is actuated when sound, or voice, energy above a certain threshold is sensed by the transducer.
Note: A vox is used to eliminate the need for push-to-talk operation of a transmitter by using voice energy to turn on the transmitter. Synonyms voice operated relay circuit, voice operated… (Read More →)

VoIP Positioning Center

Voice Profile for Internet Mail

Virtual Private LAN Service

Virtual Private Network

Virtual Routing and Forwarding

Abbreviation for vestigial sideband. See vestigial sideband transmission.

Virtual Service Operations

Video Service Provider

Abbreviation for voltage standing wave ratio.

VDSL Transmission Unit, Intermediate

VDSL2 Transceiver Unit at the Optical Network Unit

1. VDSL2 Transceiver Unit at the Remote Site,
2. VDSL Transmission Unit, Remove.

Abbreviation for volume unit.

1. In communications security, see susceptibility.
2. The extent to which a system will degrade when subjected to a specified set of environmental conditions.
3. In communications interference, see susceptibility threshold.
4. In cryptology, the point of weakness within the encrypted system where threats can occur, such as equipment, facilities, hardware, software, operating systems and personnel. [After X9.49]
5. [A]… (Read More →)

1. The systematic examination of a system to identify those critical infrastructures or related components that may be at risk from an attack and the determination of appropriate procedures that can be implemented to reduce that risk.
2. [The] systematic examination of an information system (IS) or product to determine the adequacy of security measures. identify security deficiencies, provide data… (Read More →)

Flammability rating established by Underwriters Laboratories for wires and cables that pass a specially designed vertical flame test formerly designated FR-1.

Voice Extensible Markup Language