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To use the glossary, simply click on the first letter of
the term of interest below:
U-V
- UPS
- Uninterruptible Power Supply. A secondary power supply that provides service when the main AC power degrades or fails. A UPS may include batteries or a motor generator (MG) set with flywheel energy storage (a no-break system).
- V.11
- ITU-T rec. describing electrical characteristics for balanced
double-current interchange circuits operating at data signaling rates up to 10
Mbps.
- V.24
- ITU-T rec. listing definitions for interchange circuits
between terminal equipment (DTE) and data circuit-terminating equipment
(DCE).
- V
- Vertical, Volts, Velocity
- VAPC
- Vector Adaptive Predictive Coding. A proprietary audio coding algorithm primarily intended for use at the lowest transmission aggregate bit rates.
- VDSL
- Video (or Very-high bit rate) Digital Subscriber Line, the fastest form of xDSL, it provides asymmetrical full duplex connectivity at 52 Mbps to the subscriber and 16 Mbps from the subscriber, over distances of up to 1.2 Km (0.75 miles) over a single pair. This type of
transmission does not support telephony over the same physical pair as do ADSL and RADSL.
- Video Server
- An audio and video file server, often with multiple terabyte hard disk capacities, connected to LANs and WANs with high-speed facilities like ATM or FDDI. Depending on use, may employ H.320, H.323, MPEG2, MPEG4 or Motion-JPEG video compression for broadcasting, training on demand to the
desktop and many other corporate purposes including marketing. Also a key technology for VoD (which see).
- VIRIS
- A BellCore-developed VIdeo Reference Impairment System, a subset of RISV, useful for determining acceptable impairment levels for compression schemes including MPEG1, MPEG2 and MPEG4, H.320, H.323 and others. VIRIS may be used as the preparatory phase of a P.910 subjective testing
program.
- VoD
- Video-on-Demand, a combination of video servers, networks, infrastructure, supporting software and user interface to provide broadcast, pay-TV, training or reference data on demand. Some applications also use IRD hardware as a user terminal.
- VoDSL
- Voice over Digital Subscriber Loop, techniques permitting transmission of telephony over DSL.
- VoIP
- Voice over Internet Protocol, a series of techniques permitting transmission of telephony over the Internet. Often makes use of ITU-T G.7xx audio compression recommendations.
- VPN
- Virtual Private Network. A network that appears to its users as a private network although it may be made up of both private and public segments. A VPN may provide bandwidth on demand or provide fixed bandwidth facilities.
- VSAT
- Very Small Aperture Terminal, referring to satellite earth stations with small antenna diameters, often intended for transportable applications.
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