Index - A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A-Z
VALUE-ADDED NETWORK SERVICE (VANS) - A data transmission network routing transmissions according to available paths, assures that the message will be received as it was sent, provides for user security, high speed transmission and conferencing among terminals. Closely akin to courier services or shipping forwarders in physical commerce.
VERTICAL - Descriptive of the "vertical side" of a North American wire distributing frame, on which terminal blocks for cables are mounted vertically, as opposed to the horizontally-mounted blocks on the equipment side of the frame. Frames of vertical-only blocks are not uncommon at intermediate cable connection points between main frames, hence the term Vertical Intermediate Distributing Frame, or VIDF. Compare: HIDF. English colloquial: VERT; VERTS.
VIA NET LOSS (VNL) - The earlier Bell plan for allocating a fixed amount of loss per mile on long-haul telephone trunks and certain fixed losses to shorter circuits in order to realize a nationwide transmission plant with the lowest possible loss while minimizing echoes and "singing" circuits.
VIDEOTEX - Interactive version of teletext, with a return channel using variable forms of low-speed data. English "Prestel" typifies one realization of videotex.
VIRTUAL CIRCUIT - in packet switching, network facilities with the appearance of a dedicated private line, even though individual packets may constantly be taking variable routes.
VOCODER - an early form of digital speech coder, consisting of a speech analyzer and synthesizer. While unsuccessful in its experiments for general public communications, it became the basis for numerous speech encryption devices because its output could be run through cryptographic equipment to create secure voice communications.
VOICE CONNECTING ARRANGEMENT (VCA) - An interface arrangement provided by the telephone company to accommodate the connections of non-carrier provided voice terminal equipment to the public switched telephone network. Also called Protective Connecting Arrangement (PCA).
VOICE FREQUENCY (VF) - Any of the frequencies in the band 300-3,400 Hz which are transmitted in telephony systems to reproduce human speech voice with reasonable fidelity. Some Oriental languages have less than satisfactory results with this narrow a band, and emerging ISDN implementations are increasing it for them.
VOICE GRADE CHANNEL / VOICE GRADE FACILITY (VGF) - A line suitable for voice, low-speed data, facsimile, or telegraph service. Generally, it has a frequency range of about 300-3000 Hz.
VRC / VERTICAL REDUNDANCY CHECKING - Synonomous with Parity Checking (which also see).
VTAM / VIRTUAL TELECOMMUNICATIONS ACCESS METHOD - IBM's communications I/O control programming software that unburdens the central processor from most routine communications functions; requires a subsidiary processor in its telecommunications adapters running a program called Network Control Program (NCP).