Glossary of Terms

V

V.14
Transmission of start-stop characters over synchronous bearer channels.

V.24
Serial interface.

V.24/RS232
Standard for serial interface data transfer between data terminals and data transmission equipment.

V.25 ter
Serial asynchronous automatic dialling and control.

V.34
A modem operating at data signalling rates of up to 33 600 bit/s for use on the general switched telephone network and on leased point-to-point 2?wire telephone-type circuits.

V.42
Error-correcting procedures for DCEs using asynchronous-to-synchronous conversion.

V.42 bis
Data compression procedures for data circuit terminating equipment using error correction procedures.

V.8
Procedures for starting sessions of data transmission over the general switched telephone network.

V.8 bis
Procedures for the identification and selection of common modes of operation between DCEs and between DTEs over the general switched telephone network and on leased point-to-point telephone-type circuits.

V.80
In-band DCE control and synchronous data modes for asynchronous DTE (not to be confused with V.90).

V.90
A digital modem and analogue modem pair for use on the Public Switched Telephone Network (PSTN) at data signalling rates of up to 56 000 bit/s downstream and up to 33 600 bit/s upstream.

V.xxx
ITU V series recommendations - Data communication over the telephone network.

VAD
Voice Activity Detection. LCD such as the name or number (or both) of the person calling.

VAR
Value Added Reseller.

VDSL
Very high data rate Digital Subscriber Line. Modem using twisted-pair access operating at data rates from 12.9 to 52.8 Mbits/s.

Vector Quantization
A form of lossy compression that involves approximating groups of values in an image to a smaller set of representative values.

VESA
Video Electronics Standards Association. Organisation that sets interface standards for PCs (www.vesa.org).

VGA
The minimum standard for computer video screen displays.

VLIW
Very Long Instruction Word. A computer architecture that reads a number of instructions at the same time and executes them simultaneously.

VME
Virtual Machine Environment. Open operating system standard developed by ICL.

VOB
Voice over Broadband.

Voicemail
A computerised telephone answering system that digitises incoming voice messages and stores them on disk or flash memory. It usually provides auto attendant capability, which uses pre-recorded messages to route the caller to the appropriate person, department or mailbox. Voice mail systems may also offer directory lookup by name.

VoIP
Voice over Internet Protocol. Generic name for transmission of real-time two-way voice data over an IP network. May use H.323 or SIP protocol.

VPN
Virtual Private Network. A secure tunnel across a public network (typically the internet).

VPN Gateway
A system that provides access between two or more networks; gateways are typically used to connect networks that are dissimilar.

VRAM
Video RAM. Type of computer memory specifically designed for video display. It is faster than conventional DRAM and allows simultaneous reading and writing

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