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Glossary

Note: The Cray Communications Pocket Book Collection provided several of these explanations and definitions.

ADPCM

Adaptive DPCM (where DCPM is differential PCM, transmitting value differences, and adaptive means dynamically adjusting parameters to the data stream).

ATM

Asynchronous Transfer Mode networks (based on packet switching). A mode of data transfer in which units of data are not time-related to each other.

B-ISDN

Broadband ISDN. A communication channel having a bandwidth greater than a voice-grade channel 1 and therefore capable of higher- speed data transmission.

CBT

Computer-based training.

CCD camera

Charged Couple Device camera.

CCIR

International Radio Consultative Committee.

CCITT

International Telegraph and Telephone Consultative Committee. A standards body concentrating on definition of European Communications Standards.

CELP

Code Excited Linear Prediction. The most common vocoder technology in use today, which uses "codebooks" to quantise the input signal. The CELP algorithm provides excellent speech quality and is well suited for tele- conferencing.

CIF

Common source Intermediate Format.

CODEC

An item of equipment containing an encoder and a decoder. A device which performs the dual function of encoding two-way analogue data and two-way digital data into analogue data.

DARPA

Defense Advanced Research Project Agency.

DMA channels

Dynamic Memory Addressing.

DSP

Digital Signal Processor.

DVI

Digital Video Interactive (Trade Mark of the Intel Corporation).

ETF

European Teleconferencing Federation.

Ethernet

A LAN transmission network utilising a bus structure, first produced by Xerox in the USA, later adopted by both DEC and Intel as well. This was later adapted to create the IEEE 802.3 and ISO 8802-3 standards.

ETSI

European Telecommunications Standards Institute. Membership is open and there are currently 135 member organisations including national administrations, public network operators, manufacturers, users and research bodies.

FDDI

Fibre Distributed Data Interface. A token passing ring network specification developed by ANSI, implementing dual optical fibre rings. The network operates at 100Mbps and can be up to 100 kilometres in length.

fps

Frames per second.

FTP

File Transfer Protocol. A protocol from the Internet Protocol Suite which provides transfer of files between two dissimilar machines.

H.320

A series of audio visual communications recommendations which were ratified by the CCITT in December 1990. The aim of the series, which applies to audio visual communications over 56/64 Kbps to 2.048 Mbps channels, is to ensure videoconferencing systems and video terminals will interconnect across any network. H.320 is an umbrella standard encompassing a series of recommendations, including:

HDTV

High definition TV (e.g. 1125 or 1250 lines).

HTTP

HyperText Transfer Protocol.

IEEE

Institute of Electrical and Electronic Engineers. An American Institute responsible for developing and publishing many communications standards.

IETF

Internet Engineering Task Force. Part of the organisation that develops Internet standards.

Internet

A vast community of computers, distributed around the world, which share common protocols (TCP/IP).

IP

Internet Protocol.

ISDN

Integrated Services Digital Network. Basically the existing telephone network using existing but upgraded switches and wiring, but all digital, giving a bandwidth for a basic call of 64 kbps. This increased bandwidth allows the transmission of high fidelity compressed audio, as well as the potential for video communication.

ISO

International Standards Organisation.

JANET

Joint Academic NETwork.

JBIG

Joint Broadcasting Information Group. Generates standards for binary image compression (e.g. faxes).

JISC

Joint Information Systems Committee (of the Higher Education Funding Councils of England, Scotland and Wales). Responsible for funding SuperJANET.

JNT

Joint Network Team. Forerunner of UKERNA.

JPEG

Joint Photographic Experts Group. Generates standards for still image compression.

LAN

Local Area Network. A system for intercommunication between computer terminals, PCs and related equipment operating within the same general area.

LIVENET

London Interactive Video Network. A hybrid network combining analogue and digital communications, with gateways to ISDN, SuperJANET, Internet and satellite.

MAN

Metropolitan Area Network. A geographically extended high-speed LAN designed to interconnect users within a city or metropolitan area.

MBONE

Multicast Backbone. A virtual network that has been in existence since early 1992. Originated from an effort to multicast audio and video from meetings of the IETF. Shares the same physical media as the Internet. MBONE today is used by several hundred researchers for developing protocols and applications for group communication. It is a co-operative, volunteer effort.

MCU

Multipoint Conferencing Unit.

MHEG

Multimedia and Hypermedia information coding Experts Group. Generates standards for multimedia data (such as integrating stills, video, audio, text, etc.).

MICE

Multimedia Integrated Conferencing for European Researchers. Co-ordinated by University College London, this project aims to provide a multi-way integrated conferencing service between a number of European pilot sites, and link them to the appropriate communities in the US.

MPEG

Moving Picture coding Experts Group. Generates standards for digital video and audio compression.

NetBIOS

Network Basic Input/Output System. A network communication system operating on MS/DOS PC networks.

NTSC

(US) National Television System Committee - TV standard.

ODA

Office Document Architecture. Defines the structure of complex documents for interchange between systems in an OSI environment. It also provides for the creation, change, consolidation and management of documents using screens or printers as necessary for input and output (ISO 8613/CCITT T.411-T.418).

OSI

Open Systems Intercoynnection. The term defined by the International Standards Organisation as a basis for standards to enable different vendor systems to interwork without modification.

OSPF

Open Shortest Path First.

PAL

Phase Altering Line. The TV standard in much of Europe which uses YUV colour space (i.e. Y luminance, 1.3 MHz chrominance components U, V).

PBX

Private Branch Exchange. PCM Pulse Code Modulation. An encoding technique for digitising analogue voice signals (used, for example, with CD audio).

PDH

Plesiochronous Digital Hierarchy.

PNO

Public Network Operator

POTS

Plain Old Telephone System.

PSTN

Public Switched Telephone Network.

QCIF

Quarter Common source Intermediate Format.

QuickTime

Produced by Apple, QuickTime is a set of protocols that allow a Mac or a PC running Windows to use a single interface to create/display/manipulate movies that contain digitised video, sound, text, etc.

RIFF

Resource Interchange File Format.

RIPE

Réseaux IP Européens. Co-ordinator of the Internet community in Europe. Operational since 1989. A RIPE Network Co-ordination Centre in The Netherlands provides Internet management functions, network software and documentation.

RTP

Real Time Protocol. A transport protocol for audio/video data that is being developed by the Audio/Video Transport working group of the Internet Engineering Task Force.

SDH

Synchronous Digital Hierarchy.

SGML

Standard Generalised Mark-up Language (mark-up metalanguage - ISO 8879).

SMDS

Switched Multimegabit Data Service.

SuperJANET

A national high performance network supporting UK education and research. It currently provides three services: a high performance IP service to all connected sites, an ATM service to a sub-set of the connected sites and a video network to the ATM sites. Super VGA High resolution VGA often 800X600 pixels and 256 colours with faster scanning rate. S-Video Separate-video (also known as Y/C) in which the luminance and chrominance information of a video signal are carried on separate wires.

T1

A digital communications path operating at 1.544 Mbit/sec.

TCP/IP

Transmission Control Protocol/Internet Protocol. Two main network communication protocols, part of the Internet Protocol Suite.

TLTP

Technology in Learning and Teaching Programme (run through UCOSDA).

Token Ring

A LAN transmission network utilising a ring structure. The most common form is IBM Token Ring. This network type is detailed by the IEEE 802.5 and ISO 8802-5 standards.

TUA

Telecommunications Users Association.

UDP

User Datagram Protocol.

UKERNA

UK Education and Research Networking Association. A company that has been set up to manage the networking programme for the UK higher education and research community.

VADPCM

Variable rate ADPCM compression.

VESA

Video Electronics Standards Association.

VGA

Virtual Graphics Adapter. Standard 640X480 resolution PC monitor configuration.

WAN

Wide Area Network. A network which uses public or private circuits to link terminals, PCs and computers over long distances that also often allows some user choice in destination. Following the implementation of routers, bridges and gateways, many LANs are becoming WANs, but more typically networks such as X.25 are classed as WANs.

WWW

World Wide Web.
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