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    vertical, volts

v & h mileage
    The vertical and horizontal mileage between two points is a
geometrically computed approximation of the actual airline miles
between two points. Central offices have an assigned set of v & h

v h coordinates
    Vertical and horizontal grid points used to determine straight-line
mileage between locations. Used for mileage-sensitive product pricing.

V Series
    A group of ITU-TS recommendations governing data transmission over
telephone lines.

    ITU-T Rec. V.11 describing Electrical characteristics for balanced
double-current interchange circuits operating at data signalling rates
up to 10 Mbit/s.

    The CCITT standard for fax transmission at 14,400bps.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 0-300 bps, full-duplex, dial-up modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 1200-bps, full-duplex, dial-up or leased-line

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 2400-bps, full-duplex, dial-up modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 600- and 1200-bps, dial-up modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) list of definitions for interchange circuits between data
terminal equipment (DTE) and data circuit terminating equipment (DCE).

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for dial-up automatic calling or answering equipment.

    Automatic calling and answering equipment on the PSTN.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 2400-bps, leased-line modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 1200- and 2400-bps dial-up modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 2400-bps, full-duplex, dial-up modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 4800-bps, leased-line modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 2400- and 4800-bps, leased-line modems.

    The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 2400- and 4800-bps, dial-up modems.

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for the electrical characteristics of interchange

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 9600-bps, point-to-point, four-wire, leased-line

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 9600-bps, two-wire, duplex, leased- and dial-up
line modems.

V.32 terbo
An industry standard for dial-up modem communications of 19.2 Kbps.

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 14.4K-, 12K-, 9600-, 7200-, 4800-bps, dial-up line

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for 14.4K-bps, point-to-point, four-wire, leased-line
modem connection.

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for data transmission at 48K-bps using 60-180KHz
wideband circuits.

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for error-correction. CCITT V.42 is primarily used in
Hayes' LAPM specification and Microcom's MNP level 4.

V.42 compatible
Modem that follows all the V.42 specifications, except for LAPM error
control (uses MNP instead).

V.42 compliant
Modem which follows all the V.42 specifications, and uses LAPM error
control or MNP error control.

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for real-time, 4-to-1 data compression with Hayes'
LAPM error correction protocol. CCITT V.42bis is based on British
Telecom's Lempel-Zev (BLT2) algorithm.

The International Consultative Committee for Telephone and Telegraph
(CCITT) standard for modem loop backs.
A name for modems capable of data speeds up to 28.800 bits per second.

See voice answer back.
voice answer back (VAB)

vacant code intercept
Routes all calls dialed with an unassigned first digit to: the
attendant, a busy signal, a "reorder" signal, or a recording.

vacant number intercept
Routes calls of unassigned numbers to the attendant, a busy signal, or
a recording.

VADS value-added data network
See value-added network (VAN)

valid transmission timer
In fiber-distributed data interface (FDDI) networks, a device that
measures the period between valid transmissions on a ring. It helps to
detect excessive ring noise, token loss, and other faults.

1) The formal process of reviewing or examining a single data element
value, a requirements specification, a user interface, an
implementation design, plan, schedule, budget, or similar system
element, confirming that it is acceptable for use. 2) The process of
searching for and eliminating errors. 3) Insuring that the payment
method given in an Operator Services call is acceptable and meets all
billing criteria void of line restrictions.

validity check
A test of the quality of transmission.

value-added carriers
Vendors that add special features to services purchased from other
carriers and resell the service.

value-added network (VAN)
A communications network that provides such additional features as
message switching and protocol handling. VAN sometimes refers to
packet-switched networks with protocol conversion to correct dissimilar
system interface capability. See other common carrier and specialized
common carrier. value-added network service (VANS) 1) A communications
company that uses e common carrier networks for transmission, but
supplies enhanced data features by way of specialized equipment.2) A
data transmission network that routes messages according to available
paths, assures that the message will be received as it was sent and
provides for user security, high speed transmission and conferencing
among terminals.

See value-added network. vanity number A specific 800 or local
telephone number that may spell a significant word or message with
assigned alpha characters.
value-added network (VAN)

See value-added network service.

See vector adaptive predictive coding.
vector adaptive predictive coding (VAPC)

Products announced but not yet commercially available. Often used by
suppliers to lock users in with the promise of great things to come.

A quantity that can assume any of a given set of values.

variable-length record
A record whose length depends on other related records.

See Virtual Address eXtension (VAX)

See virtual circuit or virtual container.
virtual circuit (VC)
virtual container (VC)

See voice connecting arrangement (VCA)

VCC See virtual channel connection.
virtual channel connection (VCC)

VCI See virtual circuit identifier.
virtual circuit identifier (VCI)

VCR See video cassette recorder.
video cassette recorder (VCR)

VDT 1) video display terminal; see cathode ray tube. 2) See video dial
cathode-ray tube (CRT)
video dial tone (VDT)

See visual display unit (VDU)

vector adaptive predictive coding (VAPC)
An audio coding algorithm primarily for use at the lowest transmission
aggregate bit rates.

vendor independent messaging (VIM)
Standard for the application interface to e-mail from Lotus,
WordPerfect and others. It will include MAPI compliance.

verified account codes
A finite list of carrier-verified, predefined account codes.

See Very Easy Rodent-Oriented Netwide Index to Computerized Archives

A provider of tax jurisdiction rate tables and related software.

vertical redundancy check (VRC)
In ASCII-coded blocks, the parity test (even or odd) performed on each
character in the block. See parity check.
parity check

Very Easy Rodent-Oriented Netwide Index to Computerized Archives
A search tool, like Archie, that searches text in Gopher menus.

very high frequency (VHF)
1) The frequencies between 30 MHz and 300 MHz. 2) The television
channels between 2 and 13.

very large scale integration (VLSI)
Over 10,000 transistors per chip See large scale integration.
large scale integration (LSI)

very low frequency (VLF)
The frequencies below 30 KHz.

very small aperture terminal satellite (VSAT)
A terminal used in individual corporate communications. VSAT consists
of one master earth station (MAS) and numerous two-way satellite
terminals. VSAT technology is widely used by oil companies and other
multinational firms for nationwide data, voice, and fax transmission.

See voice frequency (VF)

VF access
Voice frequency access is an option on DS-0.

See voice grade (VG)

See video graphics array (VGA)

See voice-grade data facility.

See voice grade equivalent

See voice grade facility (VGF)

See very high frequency (VHF)

via net loss (VNL)
The lowest loss, in decibels, at which a trunk facility can operate.
Contributing factors are echo, crosstalk, noise, and singing.

Microsoft's Video For Windows program to capture video input to ram or
hard disk memory.

1) Animated image transmission, storage, and display. 2) The portion of
the frequency spectrum used for TV signals. A signal with a bandwidth
of approximately 5 MHz is generated from TV scanning.

video capture board
An expansion board you put inside a PC that allows you to capture a
single frame from an NTSC source and save it on your hard disk.

video cassette recorder (VCR)
An analog magnetic recording and playback machine. Generally used for
recording and viewing full-motion video.

video conference
A conference between two or more remote locations with live, animated
image transmission and display. Two-way video conferencing allows both
locations to see the people and presentation materials at the other

video conferencing
Video conferencing introduces new requirements to the ordinary transfer
of video information. The first requirement is guaranteed minimum
latency, because to sustain a moving image, the next frame of
information must get to the other end soon enough to avoid image
freeze. In practice, the image information is highly compressed and the
effects of delayed information in a video sequence is less than the
effect on voice transmission. The second requirement is
synchronization. Video conferencing includes voice and other media such
as electronic chalkboard. It is important that the sound replay matches
the image. Equally, when an image is written on the pad, the
information on the electronic chalkboard should appear at the same
time. The third requirement is broadcast capability. An efficient
method of transmitting to multiple sites simultaneously is required
when the conference involves more than two parties.

video conferencing standards
ITU-TS H.261 was the standards watershed. Announced in November 1990,
it relates to the decoding process used when decompressing
videoconferencing pictures, providing a uniform process for codecs to
read the incoming signals. Originally defined by Compression Labs Inc.
Other important standards are H.221: communications framing; H.230
control and indication signals and H.242d: call set-up and disconnect.
Encryption, still-frame graphics coding and data transmission standards
have still to be developed.

video dial tone (VDT)
1) Provides video to offices and houses without affecting the content
of the video signal. 2) The visual counterpart to basic exchange
service audio dial tone whereby video information is switched over a
public network. As with audio dial tone, VDT can be used to connect one
or more locations for the transmission and exchange of visual and
auditory information.

video disk
A record-like device that is capable of storing large amounts of audio
and video data.

Video for Windows
A software program that lets users play video on their PC without
additional hardware.

video graphics array (VGA)
The standard IBM PC video display. Provides medium resolution text and
graphics. VGA pixel resolution is 640X480.

video pass through
A television or other video source connected to the computer to play
video on the computer screen.

video server
An audio and video file server with hard disk capacities often measured
in the terabytes, connected to LANs and WANs with high-speed facilities
like ATM or fiber-distributed data interface (FDDI) . Usually uses
H.320, MPEG or Motion-JPEG video compression. Used for training on
demand to the desktop and many other purposes including marketing and

video signal
The electromagnetic frequency needed to transmit moving pictures,
requiring one to six MegaHertz.

A technology that allows individuals to retrieve, via a television set
or a computer, video material stored in a remote database when one
wants it (i.e., on demand). The material, which can include films,
training videos, or any other video information, can be viewed (at any
time) by an individual and manipulated with VCR-like controls (i.e.,
pause, rewind, fast forward). The same material can also be viewed
simultaneously by different people in different locations, allowing
them to watch the same or different portions of the video at the same

The default video compression algorithm in Microsoft's Video For
Windows. Can produce 8 or 16 bit video sequences.

An information service that uses a slightly modified domestic
television receiver in conjunction with a normal public telephone line
to provide an interactive, computerized data-retrieval service for
homes and offices. Synonym: viewdata

See videotex

See vendor independent messaging.
vendor independent messaging (VIM)

Banyan Systems' Virtual Networking operating system is based on Unix
system V. This network operating system provides transparent
communication across heterogeneous networks and is more expansive in
concept, although attracting far fewer users, than Novell's NetWare.

Virtual Address eXtension (VAX)
1) Digital Equipment's computer systems. 2) The family of DEC computers
that host Hekimian's REACT 2000 Operations Support System.

virtual channel connection (VCC)
The basic unit of switching in BISDN. Set up between two end users
through the network, and a variable-rate, full-duplex flow of
fixed-size cells is exchanged over the connection.

virtual circuit (VC)
A communications channel that provides for the transport of
asynchronous transfer mode (ATM) cells between two or more endpoints
for the purpose of user-user, user-network, or network-network
information transfer. The connection may use different circuits during
a transmission, but behaves as a dedicated path.

virtual circuit identifier (VCI)
In cell relay systems, VCI permits networks to assign a fixed route for
all frames between network end-points by simple "table look-up"

virtual collocation
The provision of service in a manner intended to provide many of the
benefits of an actual, or physical, collocation. This is used primarily
to refer to collocation in a local exchange carrier (LEC) office. The
customer generally can select the type of equipment used in the central
office, but the equipment is owned and maintained by the LEC.

virtual company
A company built on the basis of teleworking with limited central office
administration. Made possible by improved communications and groupware
software, it is a phenomenon of the future.

virtual container (VC)
SDH defines a number of Containers, each corresponding to an existing
plesiochronous rate. Information from a plesiochronous signal is mapped
into the relevant container along with control information known as the
"path overhead". The container plus path overhead form a VC.

Virtual LAN
A logical rather than a physical LAN comprising workgroups drawn
together for business reasons or for a particular project irrespective
of each member's actual location. Members are likely to belong to
several such LANs as their job function dictates. Such LANs await the
maturity of high-speed transmission technologies such as ATM before
they can exist in any viable form.

Virtual Memory System (VMS)
One of the computer operating systems for Hekimian's REACT 2000 OSS.

virtual private line
Service that is functionally equivalent to a private line, but which
uses common circuits rather than dedicated circuits. Includes AT&T's
Software Defined Network (SDN) service, MCI's Vnet, and Sprint's
Virtual Private Network (VPN).

virtual private network (VPN)
A switched network with special services such as abbreviated dialing,
which allows customers to call between offices in different area codes
without dialing all eleven digits. Carriers are enhancing VPN service
offerings by bundling inbound and outbound services under one package.
This means customers can take advantage of larger volume discounts. See
software-defined network and virtual private line.

virtual reality (VR)
VR is technology that lets the user navigate and view a
three-dimensional world in real time with six degrees of freedom
(6DOF). The 6DOF represent the software's ability to define and the
hardware's ability to recognize six types of movement:
forward/backward, up/down, left/right, pitch up/down, angle left/right,
and rotate left/right. Virtual reality replicates physical reality and
is defined by interactivity and enhanced by interfacing. The visual
interface may be a head-mounted display (HMD) or cave automatic virtual
environment (CAVE), either of which replaces the normal view of space
with a virtual space that changes with movement. A virtual space can
simulate real space or a set of 3-D objects overlaid on real space.
Applications include architectural walk-throughs and flight simulation.
VR represents a new way for humans to interact with computers. It
replaces familiar output and input devices (monitors, keyboards, mice)
with hardware designed to take advantage of the way humans interact
with the physical world. The software places the user inside
interactive, three-dimensional "virtual worlds" populated with beings
and objects that react to user input. virtual storage address See
memory location.
memory location

virtual teams
Ad hoc groups of users formed to solve particular problems without
taking them away from their desks. A useful option made feasible with

virtual telecommunications access method (VTAM)
A mainframe software interface to data communications devices. VTAM is
used by IBM's system network architecture (SNA).

Virtual Telecommunications Network Service
Integrated service packages provided by AT&T under Tariff 12.

A destructive computer program that replicates itself throughout a
network. Viruses can delete files, create erroneous data, slow system
operation, and prevent applications from saving files. See worm.

visual display unit (VDU)
A device, such as a television screen, which produces a visible display
of data. It is usually equipped with a keyboard to allow communication
with a computer. A hard copy of the images produced on the screen may
be reproduced using a printer.

visually-impaired attendant service
A service that extends normal visual signals onto an attendant console
with special tactile devices and/or audible signals, allowing a
visually impaired person to function as an attendant.

See very low frequency (VLF)

VLSI very large scale integration
See large scale integration (LSI)

See Virtual Memory System (VMS) or voice message service (VMS)

See via net loss (VNL)

voice answer back (VAB)
Provides voice responses to inquiries made from telephone-type
terminals. The audio response is composed of a limited, digitized voice
vocabulary, prerecorded on a magnetic drum or disk file and produced by
an audio response unit and a computer.

voice band
See voice-grade channel

voice connecting arrangement (VCA)
An interface arrangement that accommodates the connections of
non-carrier provided voice terminal equipment to the public switched
telephone network. VCAs are provided by a telephone company

voice digitization
The conversion of analog voice signals into binary or digital signals
for transmission or storage.

voice frequency (VF)
Any frequency in the 300-3,400 Hz range that reproduces the voice with
reasonable fidelity.

voice grade (VG)
An access line suitable for voice, low-speed data, facsimile, or
telegraph service. A line with a frequency range of about 300-3000 Hz.

voice grade channel
A channel or line offering the minimum bandwidth suitable for voice
frequencies, usually 300bit/s to 3.4Kbit/s.

voice grade equivalent
The usable capacity of a digital circuit divided by 64 Kbps, as in the
number of DS-0 channels that can be derived from the circuit.

voice grade facility (VGF)
A circuit designed to direct distance dialing (DDD) network standards,
that is suitable for voice, low-speed data, facsimile, or telegraph

voice grade line
See voice grade channel

voice mail
An automatic answering service with the ability to record and replay
messages. Unlike simple answering machines, voice mail uses a
programmable computer system with options such as temporary call
routing, monitoring, and reporting.

voice mail box
The assignment of one user or number on a voice mail system.

voice mail module interface
A feature that facilitates voice message recordings for later

voice message service (VMS)
A leased service that allows a telephone user to access a voice mail
system and leave a message for a particular person.

voice paging
See paging

voice paging access
Gives attendants and telephone users entry to loudspeaker paging

voice print
Used like a fingerprint, a voice print identifies an individual by the
individual's unique voice pattern.

voice recognition
A program that learns to recognize a human voice and acts on the spoken

voice response (VR)
The handling of calls by a computerized voice. For example, an operator
may hand off a call to a voice response system, which will provide a
customer with information. (See personalized response system.)
personalized response system (PRS)

voice response unit (VRU)
A device that is able to produce a spoken message from a selection of
stored words.

voice store-and-forward (VSF)
A private branch exchange (PBX) feature that permits the storage and
system-remote retrieval of messages.

voice synthesis
computer-generated voice

voice-activated dialing
A telephone feature that allows the user to dial a number by speaking
the number into the telephone.

voice-grade channel
A channel with bandwidth equivalent to a telephone channel obtained
through the public telephone network. Voice grade channels are suitable
for transmission of speech, digital or analog data, or facsimile. Voice
grade channels generally have a frequency range of about 300 to 3000

voice-grade data facility (VGDF)
A circuit with an approximate bandwidth of 300Hz to 3400Hz, suitable
for data transmission, remote metering, supervisory control, and
miscellaneous signaling purposes.

voice-grade device
A communications channel that is usually 4000Hz, and can pass voice
sounds in the band 300Hz to 3000Hz.

voice-grade facility (VGF)
A circuit designed to direct distance dialing (DDD) network standards.
VGF is suitable for voice, low-speed data, facsimile, or telegraph

An individual cartridge or reel of tape used in backup operations.
Often the data does not fit on one volume. In that case, multiple
cartridges or reels are used.

volume control
A control that allows the ringing, monitor, and handset volumes to be

See virtual private network.
virtual private network (VPN)

See virtual reality (VR) or voice response (VR)

See vertical redundancy check (VRC)

See voice response unit (VRU)

See very small aperture terminal satellite (VSAT)

See voice store-and-forward.

See virtual telecommunications access method (VTAM)

See Virtual Telecommunications Network Service

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Created by Jim Needham

İVector Graphics 1995

Revised: February 16, 2011
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