The following tabulation describes terms which are often used in discussions on Telecommunications Technologies. 

 

3:2 PULLDOWN: The technique used to convert 24 frames per second film to 30 frames per second video. Every other film frame is held for 3 video fields resulting in a sequence of 3 fields, 2 fields, 3 fields,2 fields, etc. (See Fields, Frames)

 

4 fsc: Composite Digital video as used in D2 and D3 VTRs. Stands for 4 times the Frequency of Subcarrier, which is the sampling rate used.

 

4:2:2: The sampling ratio used in the D1 (CCIR 601) digital video signal. For every 4 samples of luminance there are 2 samples each of the color difference signals, R‑Y (Red minus Luminance) and B‑Y (Blue minus luminance).

 

4:1:1: The sampling ratio used in the DV or DVC (Digital Video, Digital Video Tape) digital video signal. For every 4 samples of luminance there is 1 sample each of the color difference signals, R‑Y (Red minus Luminance) and B‑Y (Blue minus luminance).

 

4:2:0: The sampling ratio used in some variations of DV digital video signal. For every 4 samples of luminance there is a sample of one of the color difference signals, followed by a sample of the other color difference signal on the next luminance sample.

 

4:4:4: A sampling ratio that has equal amounts of the luminance and both chrominance channels. Can also be used for RGB sampling, the color space used in most computer programs.

 

160 (16 by 9): A wide screen television format in which the aspect ratio of the screen is 16 units wide by 9 high as opposed to the 4x3 of normal TV.

 

10 BaseT: An Ethernet network implemented on twisted‑pair cabling.

 

800 SERVICE:  A long-distance that lets toll calls be free to the caller and charged to the location being called.

 

900 SERVICE:  An information service provided through long-distance facilities.  900 service takes two forms - in one version users access recorded information like sports scores, horoscopes or weather reports; the other simple counts the calls make to a phone number and is used to measure public response.  Independent information providers contract with a long-distance carrier to obtain a 900 number.

 

3270:  A communications protocol that supports on line transaction processing and file transfer

 

56K SERVICE (DEDICATED OR SWITCHED):  56K bps service, as provided by local telephone companies or long-distance carriers, offers customers digital circuits capable of transmitting voice, data, or video at data rates of 56,000 bits per second.  With switched 56K service, the customer dials up the 56K circuit on demand and pays a per-minute rate based on actual monthly usage.

 

A‑FRAME EDIT:  A video edit which starts on the first frame of the 5 video frame (4 film frame) sequence created when 24 frame film is transferred to 30 frame video (see 3:2 pulldown). The A‑frame is the only frame in the sequence where a film frame is completely reproduced on one and only one complete video frame. Here is the full sequence. (The letters correspond to film frames.) A‑frame = video fields 1 & 2, B‑frame = video fields 1 & 2 & 1, C‑frame = video fields 2 & 1, D‑frame = video fields 2 & 1 & 2.

 

A, B, C, D, G CHANNEL GROUPS:  ITFS channels are designated in groups of four frequencies designated by these letters of the alphabet and a number, e.g., A‑1, A‑2, A‑3, A‑4

 

A‑MODE EDIT:  An editing method where the footage is assembled in the final scene order. Scene 1, scene 2,...

 

ABSORPTION:  In an optical fiber, loss of optical power resulting from conversion of that power into heat. Intrinsic causes of absorption in a fiber involve tails of the ultraviolet and infrared absorption bands.  Extrinsic components causing loss include (a) impurities, e.g., the OH-ion and transition metal ions and, (b) defect, e.g., results of thermal history and exposure to nuclear radiation.  See also:  Attenuation.

 

ABSORPTION LOSSES:  Losses caused by impurities in the transmission medium as well as intrinsic material absorption

 

ACCEPTANCE ANGLE:  Any angle measured from the longitudinal center line up to the maximum acceptance angle of an incident ray that will be accepted for transmission along a fiber.  The maximum acceptance angle is dependent on the indices of refraction of the two media that determine the critical angle.

 

ACCEPTANCE CONE:  A cone whose included angle is equal to twice the acceptance angle

 

ACCESS CHARGE:  A fee paid to a local telephone company by long-distance companies for access to and use of the local network in processing long-distance calls.  Access charges are used by local phone companies to defray the costs of local service.

 

ACTIVE PORT DIAMETER:  On a light source or detector the diameter of the area in which light can be coupled to or from an optical fiber

 

ACTUATOR:  The drive system attached to the antenna mount that automatically aims the antenna at each satellite

 

ACTIVEMOVIE:  Microsoft’s architecture for the control and processing of streams of multimedia data and software that uses this architecture to play digital video and sound.  It is intended to supersede Video for Windows.

 

ACTIVE PICTURE AREA:  The part of a TV picture that contains actual image information as opposed to sync or other data. Vertically the active picture area is 486 lines for NTSC and 576 lines for PAL. The inactive area is called blanking.

 

ADDRESSABLE:  Able to control individual subscriber decoders through the use of digital computer addressing, e.g. 00100011001

 

AD HOC TELECONFERENCE:  Refers to a teleconference that uses facilities that link together for a specific event

 

ADI:  Ancillary Data Interface - A module used with the D/I to extract the data information from or insert data information into the DS-3 format

 

ADM:  Add-Drop Multiplexer - A piece of equipment which allows dynamic software-controlled configuration of circuits in a digital switched network.  An ADM is specific to the SONET environment and functions much like a "Northern Telcom 445" in a nonSONET environment.

 

ADVANCED BROADBAND NETWORK:  A telecommunications network that offers high bandwidth digital communications, and is capable of carrying voice, data, and video

 

AES/EBU: The digital audio standard set by the Audio Engineering Society and European Broadcast Union and used by most forms of digital audio from CDs to D1.

 

AGC:  Automatic Gain Control

 

AI:  Artificial Intelligence - A computer system capable of "intelligent" action

 

AIM:  See Ascend Inverse Multiplexing protocol

 

ALA:  American Library Association

 

ALGORITHM:  In audio and video coding, the step-by-step procedure (often including repetition) that provides suitable compression for the specific application.  This mathematical process results in a significant reduction in the number of bits required for transmission and may be either loss less or lossy

 

ALIASING: Defects in the picture caused by too low a sampling rate or poor filtering. Usually seen as "jaggies" or stair steps in diagonal lines.

 

ALSS:  Adult Learning Satellite Service

 

AM:  Amplitude Modulation ‑ Encoding a carrier wave by variation of its amplitude

 

AMI:  Alternate Mark Inversion - A line encoding scheme for transmitting data bits over T1 transmission systems

 

AMPLIFIER:  An electrical device used to strengthen audio or video signals or radio frequency (RF) energy

 

ANA:  Automatic Network Analyzer - Test equipment used to calibrate an RF device to tight tolerances

 

ANALOG/DIGITAL:  Two opposite kinds of communications signals.  Analog is the continuously varying electrical signal in the shape of a wave (such as a radio wave), transmitted electronically in a form analogous to the spoken work.  Digital is based on a binary code in which the picture or audio information is sent as a series of "on" and "off" signals; it is more precise and less subject to interference than analog.

 

ANALOG TRANSMISSION:  A continuous wave transmission expressed by bandwidth, or range of frequencies.  Broadcast television, cable television and AM/FM radio are transmitted on analog channels.

 

ANALOG VOICE GRADE SERVICE:  Available in either 2-wire or 4-wire configurations.  Applications:  analog circuit transmission at customer designated locations for either voice or data transmission.

 

ANGLE OF INCIDENCE:  The angle between an incident ray and the normal to a reflecting or refracting surface.  See also:  Critical angle; Total internal reflection.

 

ANGSTROM (A):  A unit of optical wavelength (obsolete). 1 A = 10^-10 meters.  Note:  The angstrom has been used historically in the field of optics, but it is not an IS (International System) unit.

 

ANGULAR ALIGNMENT:  The alignment of two optical fibers with respect to the angle formed by their axis

 

ANGULAR MISALIGNMENT LOSS:  The optical power loss caused by angular deviation from the optimum alignment of source to optical fiber, fiber-to-fiber, or fiber-to-detector.  See also:  Extrinsic joint loss; Intrinsic joint loss; lateral offset loss.

 

ANTENNA:  A structure used to receive or transmit radio or television signals, i.e. a satellite dish

 

ANTENNA GAIN:  Proportional to the effective area of an antenna; relates to the increase in radiated available power with relevance to an isotropic (point) radiator or dipole

 

ANTI‑ALIASING: The process of removing aliasing artifacts.

 

APPLICATION:  Functional system made up of software, hardware, or combination of both that performs some useful task.  Database managers, spreadsheets, word processors, videoconferencing systems, LAN's, fax machines, etc., are examples of applications.

 

ARPANET:  Advanced Research Projects Agency Network, created by the Department of Defense circa 1973

 

ARTIFACT:  A visual effect caused by an error or limitation in the system.

 

ASCII:  American Standard Code for Information Interchange - Common code for alphanumeric characters; this code enables communication among different computer systems

 

ASCEND INVERSE MULTIPLEXING (AIM):  An in-band protocol used to manage to interconnection of two remotely located inverse multiplexers.  AIM is a feature-rich, widely-used inverse multiplexing protocol developed and supported by Ascend Communications.

 

ASPECT RATIO:  The rectangular dimension of visuals used in television, 3 units of height to 4 units of width.  The ratio of width to height in a picture. Theater screens generally have an aspect ratio of 1.85 to 1, widescreen TV (16x9) is 1.77 to 1, and normal TV (40) is 1.33 to 1.

 

AST: Automatic Scan Tracking - Ampex technology which provides “slow motion” capability on professional VTRs and DTVRs.

 

ASYNCHRONOUS/ASYNCHRONICITY:  "Time‑independent" ‑‑ the capability of a communications technology to store and record programming for later playback (e.g. VCR's, microcomputers), making scheduling less crucial

 

ASYNCHRONOUS TRANSFER MODE (ATM):  A high bandwidth, controlled-delay fixed-size packet switching and transmission system; fixed-size packets are also known as "cells"; ATM is often referred to as "cell relay".  ATM will provide the bases for future broadband ISDN standards.

 

ATM:  See Asynchronous Transfer Mode

 

ATTENUATION:  Signal level loss over distance or through a two-port device, or the loss in power of electromagnetic signals between transmission and reception points

 

ATTENUATION COEFFICIENT:  A factor expressing optical power loss per unit of length, expressed in dB/km.

 

ATTENUATION-LIMITED OPERATION:  The condition prevailing when the received signal amplitude (rather than distortion) limits performance.  See also:  Bandwidth-limited operation; distortion-limited operation

 

AUDIO:  Sound energy which codes information understandably to a human listener

 

AUDIO CONFERENCE:  A telephone conference call using special equipment to maintain the strength of the signal among all parties

 

AUDIOGRAPHICS:  The simultaneous transmission of voice and computer graphics over ordinary phone lines.  This allows voice and graphics interaction among participants.  Graphics may be drawn with a variety of utilities:  sketch pad, mouse, scanned in, or video camera.  It can be created ahead of time and stored like a slide show or transferred from CAD.  It allows for a high degree of action, since several sites may interact at one time.

 

AUDIOTEX:  A database‑access system in which users employ touch‑tone telephones to access electronically stored and delivered libraries of short audio messages

 

AUDIO SUBCARRIER:  The carrier wave that transmits audio information between 5 MHz and 8.5 MHz on a satellite broadcast

 

AUTO ASSEMBLY: An edit in which an off‑line edit decision list is loaded into an on‑line edit computer and all the edits are assembled automatically with little or no human intervention.

 

AUTOMATIC ATTENDANT:  Partially interactive call answering system allowing self-transfer of calls to appropriate departments or people

 

AUTOMATIC CALL DISTRIBUTION (ACD):  A computer technology for dispatching incoming business calls to different desks or other locations where the phone can be immediately answered by a person or by a computer system that takes messages

 

AUTOMATIC CONTENT DISTRIBUTION:  Replicates and dispatches content to local workgroup servers, localizing bandwidth consumption and enabling scalability.

 

AVALANCHE PHOTODIODE (APD):  A photodiode that shows gain in its output power compared to the optical power that it receives through avalanche multiplication of photocurrent.  Note:  As the reverse-bias voltage approaches the breakdown voltage, hole-electron pairs created by absorbed photons acquire sufficient energy to create additional hole-electron pairs when they collide with ions; thus, a multiplication (signal gain) is achieved.  See also:  Photon; PIN photodiode

 

AVI:  Audio Video Interleaved:  The Video for Windows file format for digital video and audio.

 

AXIAL RAY:  A light ray that travels along the optical fiber's axis.  See also:  Meridional ray: Skew ray

 

AZIMUTH:  A compass bearing measured in degrees, minutes, and seconds relative to true or magnetic north

 

B‑MODE EDIT: An editing method where the footage is assembled in the order it appears on the source reels. Missing scenes are left as black holes to be filled in by a later reel. Requires fewer reel changes and generally results in a faster edit session.

                     

B8ZS:  Binary Eight Zero Suppression - An encoding scheme for transmitting data bits over T1 transmission systems

 

BACKSCATTERING:  That portion of scattered light which returns in a direction generally reverse to the direction of propagation.  See also: Rayleigh scattering; Reflectance; Reflection

 

BACKUP:  The process of creating a copy of computer data on an external storage medium, such as a floppy disk, tape, or external hard drive.  If the external storage medium is remotely located, some form of data communications channel must be established between sites.

 

BANDWIDTH:  The range of frequencies over which signal amplitude remains constant as it is passed through a system, or, a measure of the information carrying capacity of a communications channel, or the amount of the electromagnetic spectrum that a given signal occupies; the higher (wider) the bandwidth, the greater the information; usually expressed in Kilohertz (thousands of Hertz, or KHz) or Megahertz (millions of hertz, or MHz)

 

BANDWIDTH-LIMITED OPERATION:  The condition prevailing when the system bandwidth, rather than the amplitude (or power) of the signal, limits performance.  The condition is reached when material and modal dispersion distort the shape of the waveform beyond specified limits.  See also:  Attenuation-limited operation; Distortion-limited operation; Material dispersion; Modal dispersion.

 

BASEBAND:  Video or audio information that modulates a low IF frequency

 

BAUD RATE:  The speed at which data is communicated (approximately equal to bits per second); most commonly 300, 1200 and 2400 baud for ASCII computer messaging services

 

BEAM BENDER:  Booster amplifier that increases on-channel signal level

 

BEAM DIAMETER:  The distance between two diametrically opposed points at which the irradiance is a specified fraction of the beams peak irradiance; most commonly applied to beams that are circular or nearly circular in cross section.  Synonym:  Beamwidth.  See also:  Beam divergence

 

BEAM DIVERGENCE:  The increase in beam diameter with increase of distance from the source

 

BEAMSPLITTER:  A device for dividing an optical beam into two or more separate beams; often a partially reflecting mirror.  See also:  Coupler; Splitter

 

BEAM TILT:  The technique of focusing antenna arrays slightly below the horizon to reach selected areas; can be electrical or mechanical

 

BEAMWIDTH:  The acceptance angle of an antenna, usually measured between half-power (3 dB) points

 

BELL SYSTEM:  A group of affiliated RBOCs (Regional Bell Operating Companies) in the United States that operates under consistent rules and specifications, many of which are set by AT&T

 

BEND LOSS:  A form of increased attenuation of optical fibers caused by radiation of high-order modes from the side of the fiber.  The two common types of bend losses are:  (a) those occurring when the fiber is curved around a restrictive radius of curvature and (b) microbends caused by small distortions of the fiber imposed by externally induced perturbations, such as poor cabling techniques.

 

BER:  BIT Error Rate - The fraction of a sequence of message bits that are in error.  A bit error rate of 10⁶ means that there is an average of one error per million bits

 

BETACAM: An analog videotape format using 12.5mm tape developed by Sony and derived from the earlier Betamax. Also includes Betacam SP (Superior Performance), and digital versions Digital Betacam and Betacam SX.

 

B-ISDN:  Broadband Integrated Services Digital Network - A digital signalling network in which equipment interface data rates operate at speeds of 155 to 622 million bits per second (MBs)

 

BI-DIRECTIONAL PREDICTION:  A form of compression in which the Indeo® video 4 codec uses information not only from frames that have already been decompressed, but also from frames yet to come.  The codec looks in two directions:  ahead as well as back.  This helps avoid large spikes in data rate caused by scene changes or fast movement, improving image quality.

 

BIRD:  Slang for communications satellite

 

BIT:  Binary Digit - A bit is the smallest and most basic unit of information used by a computer represented by a "1" or "0", or by "on" or "off".  One bit is one digital signalling element; a single alphabetic or numeric character is typically represented by 10 bits.

 

BIT:  Built-In Test - or diagnostic circuitry

 

BIT ERROR RATE (BER):  In digital applications, it is the ratio of bits received in error to bits sent.  BER's of 10 (one error bit to a billion sent) are typical

 

BITM:  Bureau of Information and Telecommunications Management, Wisconsin Department of Administration

 

BISYNCHRONOUS:  A data link protocol for synchronizing transmission of binary coded data

 

BIT RATE: The amount of data transported in a given amount of time, usually defined in Mega (Million) bits per second (Mbps). Bit rate is one means used to define the amount of compression used on a video signal. Uncompressed D I has a bit rate of 270 Mbps. Mpeg I has a bit rate to 1.2 Mbps.

 

BITNET:  A general purpose international academic data network for messaging and simple file transfer, linking over 1300 university and college computing centers in 21 countries

 

BIT STREAM: A continuous series of bits.

 

BLACK BOX: A term used to describe a piece of equipment dedicated to one specific function, also called dedicated hardware.

 

BLANKING: The part of the video signal that contains no picture information. Used for synchronizing, timecode, closed captions, etc.

 

BLOCK DOWNCONVERTING:  The multi‑conversion process of converting the entire band to an intermediate frequency (4 GHz to 1 GHz) for transmission to multiple receivers, where the next conversion takes place

 

BNC:  A type of bayonet-lock coaxial cable connector used for video and communications.  BNC is said to be short for bayonet‑Neill‑Concelman. Contrast with TNC.

 

BONDING:  Bandwidth On Demand Interoperability Group.  A Consortium of over 40 data communications equipment vendors and service providers who joined together to create a standardized inverse multiplexing protocol so that inverse multiplexers from different vendors could interoperate.  Also refers to the resultant specification, sometimes known as the "BONDING specification".

 

BOOSTER:  Typically an active amplifier without frequency conversion which repeats channels in a shadowed area.  See:  Beam Bender

 

BOWSER: Odetics video browsing system that allows the viewer to track and view the material database

 

BRI - BASIC RATE INTERFACE:  An ISDN subscriber line, consisting of two 64kbit/s B voice channels, or "bearer" channels, and one 16 kbit/s D channel, used for both data and signaling purposes

 

BRIDGE:  A device that passes packets between two similar LAN channels (e.g. Ethernet-to-Ethernet, or a device which connects three or more telecommunications channels, such as telephone lines

 

BROADBAND:  A local area network (LAN) residing on coaxial cable capable of transporting multiple data, voice and video channels.  Broadband channels have enough bandwidth to carry full motion video, stills, graphics, audio and text (e.g., fiber optics, cable television, ITFS).  It has a high-capacity communications circuit/path.  It usually implies a speed greater than 1.544Mbps.  (Contrast with wideband and narrowband).

 

BROADCAST:  Television and radio designed to reach mass audiences with an audio or video signal that is transmitted from a central point and can be reached by persons around the transmitter using standard radio or television receive equipment

 

BROADCAST QUALITY: A nebulous term used to describe the output of a manufacturer6s product. Usually at least means that the technical specifications meet the FCC rules for broadcasting.

 

BROADCAST VIDEO TV-1 SERVICE:  Provides dedicated transport of broadcast quality video signals meeting NTSC analog interface standard RS250B.  Currently available on a limited basis.  See your local Time Warner Telecom representative for details.

 

BUG: An error in a computer program. Also something that bites you on a camping trip.

 

BURNED IN TIME CODE: Time code numbers that are superimposed on the picture. Also called window bum.

 

BYTE 8 BITS:  The combination of 8 bits into 1 byte allows each byte to represent 256 possible values. (see Megabyte, Gigabyte, Terrabyte)

 

BYTE:  A group of bits, usually eight, handled as a unit by a computer operating system

 

CABLE:  Optical fiber, multiple fibers, or fiber bundle which may include a cable jacket and strength members, fabricated to meet optical mechanical, and environmental specifications.  See:  Fiber buffer; Fiber bundle

 

CAD:  Computer Aided Design - Computer drawing software that allows user to create visual representations in color, according to scale, and in multiple dimensions.  While software is applicable to a number of content areas, it offers exceptional promise in vocational education for learning automotive, drafting, electrical, landscape, and interior design

 

CAI:  Computer Assisted Instruction

 

CALLING NUMBER IDENTIFICATION:  An advanced network feature that provides users with the phone number of an incoming call as the phone is rining.  A divice attached to the phone displays the caller's number, so the user can screen against unwanted or intrusive calls.

 

CAM:  Computer Assisted Manufacturing

 

CAMERA:  The instrument which converts a visual image into electrical impulses

 

CAPTURE:  The process of digitizing the analog video signal.  See digitize.

 

CARRIER:  1) A provider of transmission capabilities available to the general public, sometimes referred to as a "common carrier" or "regulated carrier", as it is regulated by the FCC   2)  A current in a communications channel which can be modulated to carry analog or digital signals   3)  A telephone company or similar non-private telecommunications service supplier (telecommunications usage)   4)  The radio frequency wave having at least one characteristic that may be varied by modulation

 

CARS:  Cable TV relay service

 

CATV:  Community Antenna Television - A master antenna and distribution system capable of receiving, amplifying and distributing a television signal via coaxial cable to television receivers;  also known as Cable Television end user

 

C‑BAND SATELLITE TELEVISION:  Frequencies from 4 to 6 gigahertz used mainly to transmit and receive signals to and from communication satellites.  Satellites operating in the C‑Band transmit the majority of video programming for broadcast and cable use as well as telephone transmissions and other data.  (Used loosely for satellite services in the 6/4 GHz bands.

 

CBR - Constant Bit Rate: A variety of MPEG video compression where the amount of compression does not change.

 

CCITT:  Consultative Committee of the International Telephone and Telegraph Group.  This committee is working to produce the "PX64" standard for compressed video equipment, so that codecs of various manufacturers can be used together.

 

CCTV:  Closed Circuit Television - A TV system in which the transmission of the TV signal is limited to only those receivers that are physically connected to the system

 

CCS-7:  Common Channel Signaling Number 7, a method of communication between digital switches, including database access among switches; among its uses are monitoring of and accounting for networks.  Standards for CCS-7 are part of OSI

 

CD-I:  Computer Disc Interactive

 

CD-ROM: A storage technology which can be used to keep information which can be read by a computer or similar hi-tech device.  Uses the same technology as audio Compact Discs and movie Video Discs.

 

CD-V:  Computer Disc Video

 

CELLULAR RADIO:  A mobile telephone technology that improves on existing mobile phone systems by dividing a metropolitan area into a number of smaller areas or cells, each served by a small low power transmitting and receiving station.  A car traveling from one cell to another is automatically switched onto that cell's particular frequency, allowing for continuous en route phone conversations or data communications.  Each transmitting station is connected to a mobile phone switching office and the local telephone switching center.

 

CELLULAR SERVICE:  A telecommunications service that lets customers use wireless, mobile telephones to connect, via radio towers called cell cities, to the public switched network.

 

CENTRAL OFFICE:  The local phone company facility where customer lines connect to a switch for processing.  The central office provides dial tone to local telephone users.

 

CENTRAL SANDS:  Central Sands Telecommunications Consortium, an ITFS user group comprised of university, K-12 schools, and potential private institutions in the Stevens Point area

 

CentraNet SERVICES:  Optional services built into a GTE central office switch that make telephone calling easier and faster for business customers; for example, dialing only the last four digits to reach another person. Sometimes called Centrex, CentraNet Services are an alternative to customers having to own switches for handling multiple business lines.

 

CENTREX:  A widespread telephone company switching service that uses central office switching equipment to which customers connect via individual extension access lines

 

CES:  Cooperative Extension Service, UW-Extension

 

CESA:  Cooperative Educational Service Agency

 

CHANNEL:  In NTSC, a 6 MHz bandwidth of frequencies allocated for communications

 

CHANNEL BANDS FOR TELEVISION:

            Low band - VHF Channels 2 through 6

            Mid band - Cable Channels 14 through 22

            High band - Cable Channels 7 through 13

            Super band - Cable Channels 23 through 36

            Hyper band - Cable Channels 37 through 59

            UHF - Received on broadcast television Channels 14 through 83

 

CHANNEL BANK:  A piece of equipment which allows typically 24 analog circuits to be sampled and converted into digital signals having 64,000 bits/sec per channel and subsequently merged into a time-divided bit (i.e. DS-1) formal at a rate of 1.544 MBs for transmission on a single T-1 facility between two points.  Channel banks or digital multiplexers are required at both ends of each link to combine (at one end) and separate (at the other end) the component signals.  Using channel banks, slow-scan TV, data and phone signals can be sent on the same T-1 link.

 

CHANNEL COMBINER:  A passive network that combines RF signals

 

CHANNEL MAPPING:  An operator's ability to place selected input channels on any output channel for a number of selected decoders

 

CHANNEL SERVICE UNIT (CSU):  Hardware required by the telephone company to perform functions of line conditioning, signal regeneration, and remote loopback testing on a T-1 network

 

CHROMINANCE: The signal which carries the color information in video.

 

CHROMATIC DISPERSION (PSEC):  A measure of the pulse broadening due to the source spectral width (the combined effect of the material and waveguide dispersions)

 

CINEPAK:  A QuickTime codec that is commonly used for CD‑ROM video compression. Cinepak allows temporal and spatial compression, as well as data rate limiting.

 

CITSC:  CESA Instructional Technologies Services Council

 

CLADDING:  A lower refractive index material layer that surrounds the core which has a higher refractive index.  The cladding can be either glass or plastic

 

CLADDING MODE:  A mode confined by virtue of a lower index medium surrounding the cladding.  See:  Mode

 

CLADDING MODE STRIPPER:  A device that encourages the conversion of cladding modes to radiation modes; as a result of its use, cladding rays are stripped from the fiber.  A cladding mode stripper often used a material having a refractive index equal to or greater than that of the waveguide cladding to induce this conversion.  See: Cladding; Cladding mode

 

CLASS (Custom Local Area Signaling Service):  A group of calling features that enhance basic phone service. CLASS technology identifies a calling party's number so it can be used for services like automatic callback, caller identification, selective call acceptance, and call tracing.

 

CO:  Switching office; commonly referred to as central office

 

COAX, COAXIAL CABLE:  A high capacity copper‑wire cable that carries audio and video signals and radio frequency (RF) energy, consisting of an outer conductor concentric and inner conductor, separated from each other by insulating material.  It has more bandwidth than twisted pair, but less bandwidth that fiber-optic cable.

 

CO-CHANNEL:  Two television stations operating on the same channel

 

CODEC:  COder/DECoder - Digital encoding/decoding equipment that is necessary to interface analog end-user equipment (such as a television set) to digital transmission facilities.  In the case of compressed video, codecs are also used to restore some of the motion which is taken out in the compression process.

 

CODER:  Also referred to as Encoder and is that portion of the CODEC that digitizes the analog signals to be placed on the digital fiber optic network

 

COLLIMATION:  The processing by which a divergent or convergent beam of radiation is converted into a beam with the minimum divergence possible for the system (ideally a parallel bundle of rays).  See also:  Beam divergence.

 

COLOR FRAME: A sequence of four fields (2 frames) of NTSC video. Since the phase of the color subcarrier reverses every frame in NTSC (which makes the color information essentially invisible on a black‑and‑white receiver) two complete frames are required to carry a complete sequence of color information.

 

COLOR SUBCARRIER: The portion of the NTSC signal that carries the color information. Color signals are quadrature modulated onto a subcarrier of 3.579545 MHz.

 

COMBINER:  A passive device, in which optical power from several input fibers is collected to a commmon point.  See:  Coupler

 

COMMON CARRIER:  A regulated company that supplies telecommunications services to the general public on a non-discriminatory basis.  Your local telephone company is an example.

 

COMMUNICATIONS SATELLITE:  A satellite in earth orbit which receives signals from an earth station and retransmits the signal to other earth stations

 

COMPONENT VIDEO: A video signal in which the Luminance and Chrominance signals are kept separate. This requires a higher bandwidth, but yields a higher quality picture.

 

COMPOSITING LAYERING:  Multiple pictures on top of each other. A cutout or matte holds back the background and allows the foreground picture to appear to be in the original picture. Used primarily for special effects.

 

COMPOSITE VIDEO: A video signal format that includes all the visual information in one waveform, including chrominance, luminance, blanking pedestal, field, line, color sync pulses and equalizing pulses.  Allows economical broadcasting of video. Compare component video.

 

COMPOSITE VIDEO SIGNAL:  A video signal incorporating luminance, color and synchronizing information

 

COMPRESSED VIDEO:  With compressed video, instead of transmitting a series of full‑motion video frames, only the changes in moving frames are captured and transmitted.  The reconstituted image exhibits some motion, but, depending on the available bandwidth and the capacity of the transmitters and receivers, motion may appear somewhat irregular.  This effect occurs because in compressed video technology the moving areas of the image are only approximated.

 

COMPRESSION:  Methods used to substantially reduce the amount of picture information sent in a video, audio or data signal.  A video codec compresses a video signal by only transmitting information about areas of a television picture that change over time or space.

 

COMPRESSION RATIO: The ratio of the amount of data in the original data compared to the amount of data after compression. The higher the ratio the greater the compression.

 

COMPUTER MESSAGING SYSTEMS:  Include electronic mail, bulletin boards and computer conferencing.  Messaging systems involve the exchange of information between computers using telephones or other telecommunication lines and a central "host" computer that stores the messages.

 

COMPUTER CONFERENCING:  An interactive conferencing system that allows specific groups of users to enter papers, texts or comments.  Participants can reach the conferencing system with microcomputers or terminals at any time, read the materials that have been submitted by other participants since the last session, and submit their own comments.

 

CONFERENCE CALL:  A call in which ordinary telephone lines from a number of locations are linked together through the assistance of a telephone company or telephone bridge

 

CONNECTIVITY:  The ability of devices to exchange data with each other through shared connections locally or at a distance

 

CONNECTOR:  A junction which allows an optical fiber or cable to be repeatedly connected or disconnected to a device such as a source or a detector

 

CONSORTIUM:  A voluntary organization loosely affiliated for a specific purpose

 

CONTINUOUS AUDIO:  The audio connection for a switched video network which allows all connected endpoints to speak at the same time, in the same manner as an audio bridge

 

CONTROL-LEAD DIALING:  The initiation of a dialed call over the network using signals on leads within the interface cable between an application and the network access equipment; thus, an application instructs the network access equipment to dial a call by toggling one or more leads within the cable between the application and the network access equipment

 

CONTROL TRACK: A signal recorded on video tape to allow the tape to play back at a precise speed in any VTR. Analogous to the sprocket holes on film.

 

CONUS:  Contiguous United States

 

CORE:  The center dielectric in an optical fiber whose index or refraction is greater than that of its surrounding medium, usually a cladding

 

COUPLER:  A device whose purpose is to distribute optical power among 2 or more ports, or to concentrate optical power from 2 or more fibers into a single port.  Couplers maybe active or passive.  See also:  Combiner; Splitter; Star coupler

 

COUPLING EFFICIENCY:  The fraction of available output from a radiant source which is coupled and transmitted by an optical fiber.  The coupling efficiency for a lambertian radiator is usually equal to the sin²  0 max. for the optical fiber being used.  See also:  Lambertian radiator

 

COUPLING LOSS:  The power loss suffered when coupling light from one optical device to another.  See also:  Angular misalignment loss; Extrinsic joint loss; Insertion loss; Intrinsic joint loss; Lateral offset loss

 

CP:  Construction Permit

 

CPB:  Corporation for Public Broadcasting

 

CPE:  Customer Premises Equipment - Telephone equipment, such as phones, faxes, modems, and private branch exchanges (PBXs), located on the customer's premises that connect to the network but is owned or leased by the customer.

 

CPU:  Central Processing Unit of a computer

 

CPU-intensive: Used to describe processes that require large amounts of processor time. CPU‑intensive processes usually slow down other processes running on the same computer, and may not run very well, if at all, on slower computers.

 

CRITICAL ANGLE:  The smallest angle made by a meridional ray in an optical fiber that can be totally reflected from the innermost interface and thus determines the maximum acceptance angle at which a meridional ray can be accepted for transmission along a fiber

 

CROSSTALK:  1)  The unwanted energy transferred from one circuit, called the disturbing circuitry, to another circuit called the disturbed circuit  2)  Undesired power coupled into a communications circuit.  Telephone crosstalk may be either intelligible or unintelligible

 

CROSS MODULATION:  The undesirable transfer of modulation from one carrier to another

 

CRT:  Cathode Ray Tube; The technical name for a picture tube, a camera tube or the scanning tube in a flying spot telecine.

 

CRYSTAL:  Quartz frequency control device

 

CSG:  Community Service Grant

 

C-SPAN:  Cable-Satellite Public Affairs Network

 

C/T:  Carrier-to-Noise-Temperature ratio - Ratio of received carrier power level to noise level of a satellite antenna, measured in decibels

 

CTN:  CESA Teleconference Network - A four‑wire dedicated telephone system operated by a CESA.  CESAs 3, 8 and 12 have CTN systems.  CTN systems can be interconnected with ETN.

 

CUSTOMER PREMISES EQUIPMENT(CPE):  Terminal equipment located on the customer premises which connects to the telephone network

 

CUTOFF WAVELENGTH (THEORETICAL): Wavelength below which the fiber propagates more than one mode based upon theoretical propagation modeling

 

CUTOFF WAVELENGTH (TRANSMITTED):  Wavelength below which the fiber propagates more than one mode based upon an actual measurement of a 2 meter length of fiber.

 

CWETN:  Central Wisconsin Educational Telecommunications Network - A consortium of schools located near Spencer, using an interactive television network

 

D1: Digital video tape format using the CCIR 601 standard to record 4:2:2 component video on 19mm tape. Currently the highest quality video tape format generally available. The first digital video tape format, hence D1.

 

D2: Digital video tape format using the 4fsc method to record composite digital video. Uses 19mm tape and a cassette similar to D1. The second digital video tape format, hence D2.

 

D3: Digital video tape format using 4fsc composite signals like D2, but recorded on 12.5 mm (1/2‑inch) tape. The third digital video tape format.

 

D4:  Does not exist. The number 4 is considered unlucky in Japan.

 

D5: Digital video tape format using CCIR 601, 4:2:2 video. Uses the same cassette as D3. Bet you can guess why it’s called D5.

 

DAC or DCS:  Digital Cross-connect Switch - A remote device (controlled by a central site switch) which can route data, voice, or video signals to a specific destination.  A simplified example:  suppose phone lines from City A, City B, and City C go to a local DAC and then one line goes from the DAC to the central switch site at City D.  A call from City D to City A will be made by the DAC switching the call to the City A circuit.  A call from City B to City C will be switched through the DAC and will not use the line to City D (the central switch).  The advantage of the DAC is that separate phone circuits are not required from each city to the central switch site; also, this setup prevents every single call from going through the central switch site, thereby relieving traffic.

 

DARK CURRENT:  Current that flows in photodetectors when there is no incident optical power (in total darkness)

 

DATA COMMUNICATIONS:  Communications between computers, in contrast to voice transmissions between people

 

DATA RATE:  The speed of a transfer process, usually expressed in kilobytes (thousands of bytes) per second.

 

DATABASE:  Information storage system which can be searched through a number of methods to obtain specific data. The term "database" has been in the past associated with computer services, but is now used to refer to general information storage and retrieval systems (e.g. audiotex, teletext, etc.).

 

DATA PATH:  The secondary network consisting of the "overhead" bits above the 36 Mbs video channel

 

DATA PORT:  The physical and electrical protocol used by the codec and the DSU or TA to transfer data between each other.  A codec comes with either V.35 or X.21 protocol built in.  These are actually the number of CCITT international standards which specify pinning, levels, etc.  V.35 is very common for networks in North America, and X.21 is popular on European-manufactured ISDN terminal adapters.

 

DATA RATE:  Analog transmission media is specified in bandwidth (usually in Hertz) and signal to noise (usually in dB).  Since the principles behind digital transmission are so different, media are specified in different parameters.  Rather than how much analog information is passed, a digital user is concerned with how many bits per second can be sent down the channel.

 

DATCP:  Department of Agriculture, Trade and Consumer Protection

 

dB:  Decibel - A logarithmic unit used to describe ratios such as gain.  (Number of dB 10 x log (base 10) of power ratio.  So, 3 dB represents a factor of 2, 10 dB a factor of 10, 20 dB factor of 100, etc.  If an antenna has 3 dB gain over another, then it would be twice as powerful.)   The standard unit of difference of levels to permit measurement of power, voltage, or current levels in electric or electronic practices

 

dBc:  A decibel ratio with respect to a carrier

 

dBi:  dB power relative to an isotropic source

 

dBmV:  Decibels relative to one millivolt

 

DBS:  Direct Broadcast Satellite Service - Broadcast from satellite to home. (Multiple satellite entertainment and information services received via TVRO system on a subscription basis)

 

dBW:  The ratio of the power to one Watt expressed in decibels

 

DCAIN:  Dane County Area ITFS Network - An ITFS user group in the Madison area

 

DCE:  Data Communications Equipment.  As defined in the RS-232 specification, equipment to which DTE (Data Terminal Equipment) is connected, often to enable access to network facilities.  For the purposes of this seminar, DCE refers to equipment such as network access equipment, and DTE refers to application equipment, such as a videoconference terminal.

 

DCT - Discrete Cosine Transform:  A widely used method of video compression.  Also an Ampex CCIR 601 digital VTR using DCT to compress the video before recording it to tape.

 

DDR - Digital Disk Recorder:  A digital video recording device based on high speed computer disk drives. Commonly used as a means to get video into and out from computers and for editing.

 

DDS:  Digital Data System - This is the most common point-to-point, dedicated digital telephone service which works well with the codec.  The user pays a monthly charge to the phone company for a full time link, no matter how much he actually uses it.

 

DDS:  Direct Digital System - A network whose component parts and signals (representing information of various types) are all transmitted via standardized digital signalling methods.  In a DDS network, no analog-to-digital converters are necessary.

 

DECIBEL (dB):  The standard unit used to express gain or loss of optical power

 

DECLINATION:  Angle between antenna beam and equatorial plan (measured in meridian plane).  The offset angle of an antenna from its polar mount axis

 

DECODER:  A TV set-top box used to unscramble purposely scrambled television signals (unscrambles and converts incoming channels to frequencies acceptable to the subsciber's television set).  Also, that portion of the CODEC that converts the digitized signals received off the fiber optic network to analog signals.

 

DECODE:  The process of decompressing a video clip and then converting its color space of from YUV to RGB.

 

DECOMPRESS:  The process of converting video and audio data from its compact form back into its original form in order to play it.

 

DEDICATED CHANNELS:  Channels that are reserved for specific uses; government, education and public access cable channels are examples of dedicated channels

 

DEDICATED LINES:  A leased or purchased line that connects two or more data communication sites used exclusively by one vendor or user

 

DELTA FRAME:  A frame containing only the data that has changed since the last frame.  Delta frames are an efficient means of compressing image data.

 

DEMARC:  Demarcation - A line either side of which determines the Contractor's and Owner's responsibilities.  The location(s) where customer-provided equipment is connected to carrier-provided equipment.  Example:  the splice block where a telephone line enters most homes is a demarc; everything on the line side of the demarc is the responsibility of the telephone company, while everything on the home side (i.e. the house wiring and the telephones themselves) is the responsibility of the homeowner.  The WECB demarcs refer to locations where access to the backbone network is made available.

 

DEMODULATION:  The process of extracting baseband information from a modulated carrier wave

 

DESCRAMBLER:  An electronic device that decodes encrypted satellite signals

 

DETECTOR:  A transducer that provides an electrical output signal in response to an incident optical signal.  The current is dependent on amount of light received and type of device.  See also:  Receiver

 

DETIC:  Distance Education Technology Initiative Committee

 

DEVIATION:  An FM modulation parameter indicating the amount of frequency modulation

 

DEVICE DRIVER:  Software to enable a computer to access or control a peripheral device, such as a printer.

 

DHSS:  Wisconsin Department of Health and Social Services

 

D/I:  Drop and Insert - Electronic unit to drop or insert any combination of the Codec audio, DS-1 and data channels

 

DIAL TONE:  The signal the network sends when it is ready to initiate a connection

 

DIGITAL:  A form in which everything is defined by a series of numbers, usually ones and zeros (binary).

 

DIGITAL BETACAM:  Digital video tape format using the CCIR 601 standard to record 4:2:2 component video in compressed form on 12.5mm (1/2‑inch) tape.

 

DIGITAL DIAL-UP BANDWIDTH:  Communications channels created by signaling to the network from the caller's site the intended destination of the connection.  These channels may be terminated when the caller or called party chooses.  The user pays for the bandwidth only when it used.  Digital Dial-Up Bandwidth operates in a fashion similar to the dialed voice telephone network but the resultant connections are digital and of specified bandwidths.

 

DIGITAL TELECOMMUNICATIONS:  An information transmission, storage and processing method that uses electronic or optical pulses, also called bits

 

DIGITAL SIGNALS:  Digital technology converts audio, video and data into a series of "off" and "on" signals.  Digital channels are generally more precise, less subject to interference, can carry more information and can support higher transmission speeds than analog systems.

 

DIGITAL VIDEO:  A video signal represented by computer-readable binary numbers that describe colors and brightness levels.

 

DIGITAL VS. ANALOG:  An analog electrical signal (sound or light, etc.) is noted by a fundamental change in character with respect to information being conveyed; i.e. an AM radio station changes the amplitude of a carrier signal to varying degrees depending on the amplitude of the music it is carrying.  A digital signal is always in one of two states (on or off), but varying at a rate fast enough that information encoded into numbers (quantized) can be transferred.  Another way to look at the difference is that an analog signal has an infinite number of degrees of changes which convey information; a digital signal has only two.  One of the largest advantages of digital transmission is that as long as a receiver can distinguish between the two states in the signal, noise will have no effect on it.

 

DIGITAL TRANSMISSION:  While an analog signal is a continuous wave, digital transmission is a code of discrete binary signals (on and off, zero and one, high and low, etc.);  digital transmission is expressed by numbers of bits per second, or data rate

 

DIGITIZING:  The act of taking analog video and/or audio and converting it to digital form. In 8 bit digital video there are 256 possible steps between maximum white and minimum black.

 

DILHR:  Wisconsin Department of Industry, Labor and Human Relations

 

DIN:  Decision Item Narrative - An individual descriptive proposal in the budget preparation process

 

DIPLEXER:  Device that combines two transmitted signals, e.g., visual and aural carriers

 

DIPOLE:  A half wavelength element of an antenna consisting of 2 quarter wave radiators that are co-linear and center fed

 

DISASTER RECOVERY:  The use of alternative network circuits to re-establish communications channels in the event that the primary channels are disconnected or malfunctioning

 

DISH:  Slang for satellite earth station antenna

 

DISPERSION:  Distortion of an electromagnetic signal caused by different propagation characteristics of different wavelengths, and the differing path lengths of modes in a fiber.  See also:  Material dispersion; Modal dispersion

 

DISPERSION BOX:  Graphic representation showing the dispersion constants for a given laser operating wavelength range

 

DISTANCE EDUCATION (or DISTANCE LEARNING):  Instruction that takes place in a setting where the teacher is in contact with the student by means of correspondence or telecommunication technologies.  These technologies are often used to link student and teachers within or between districts and states, as well as internationally.  These technologies include broadcast and narrowcast radio and television (e.g., cable, fiber optics, ITFS, microwave, satellite, etc.) telephone, video disk, video tape, and computer applications.

 

DISTORTION-LIMITED OPERATION:  The condition prevailing when distortion of a received signal, rather than its amplitude (or power), limits performance.  The condition reached when a system distorts the shape of the waveform beyond specified limits.  In a fiber-optic system, it usually results from material and modal dispersion.  See also:  Attenuation-limited operation; Bandwidth-limited operation; Material dispersion; Modal dispersion; multimode distortion

 

DMA:  Department of Military Affairs

 

DMA:  Designated Market Area

 

DMS-100:  The model number for a large central office switch made by Northern Telecommunications.  The DMS-100 has the capability to switch other types of lines in addition to telephone lines, such as T1 circuits.

 

DNR:  Department of Natural Resources

 

DOA:  Department of Administration

 

DOC:  Department of Corrections

 

DOJ:  Department of Justice

 

DOR:  Department of Revenue

 

DOT:  Department of Transportation

 

DOWNCONVERSION:  Translation of frequency or a block of frequencies to a lower portion of the electromagnetic spectrum, e.g., from SHF (microwave) frequencies to UHF and VHF

 

DOWNCONVERTER:  A device that heterodyne converts a signal to a lower output frequency

 

DOWNLINK:  A satellite receive system that processes satellite delivered information, and includes the satellite itself, the receiving earth station and the signal transmitted downward between the two; occasionally, this word is used to refer to the TVRO dish itself

 

DOWNLOADABLE VIDEO: : Copying a file from a server to your computer using the network and storing it in memory or on a disk.  Downloadable video cannot be viewed in real-time because the video data stream exceeds the network throughput.

 

DOWNLOADING:  The process involves transferring information from one device to another over a telecommunications channel (e.g. telephone, broadcast).  Information received from the originating source can then be stored by the receiver for future use.

 

DPI:  Wisconsin Department of Public Instruction

 

DROP AND INSERT:  A process of adding data (insert) to a T1 data stream, or terminating data (drop) from a T1 data stream to over devices connected to the drop and insert equipment

 

DROP FRAMES:  To fail to play every frame in a video file, usually because of performance limitations of the systems playing the video.

 

DS-0/DS-3:  Designations given to circuits of different bit rates.  A DS-0 circuit has a bit rate of 56 KBs (actually, the full width is 64 KBs, but the rest is used for overhead associated with the transfer).  A single digital telephone circuit uses a DS-0.  A DS-3 has a bit rate capability of 45 MBs, which is equivalent to 28 T1 circuits, or 672 DS-0 circuits.

 

DS0 SERVICE:  Dedicated, full duplex digital channel with line speeds of 2.4, 4.8, 9.6, 56 or 64 Kbps.  Applications:  voice, data, image or video where high quality all-digital communications are needed.

 

DS-1:  Also called a T-1;  Dedicated, high capacity, full duplex channel with line speed of 1.544 Mbps isochronous serial data.  Line code of AMI or B8ZS and either Superframe (D4) or Extended Superframe formats.  DS1 Service has equivalent capacity of 24 Voice Grade Services or 24 DS0 Services.  Applications:  voice, data, image or video where there is a need for cost effective, bulk communications between two locations.  DS1 Service is used in hubbed networks as a backbone transport or terminated directly to high volume customer locations.

 

DS3 SERVICE:  Dedicated high capacity, full duplex channel with line speed of 44.736 Mbps isochronous serial data.  Line code of B3ZS.  DS3 Service has equivalent capacity of 28 DS1 Services at 1.544 Mbps, or 672 Voice Grade Services, or 672 DS0 Services at 56/64 Kbps.  Applications:  high volume voice, data, image or video; eliminating the need to maintain and pay for multiple dedicated lines.  DS3 Service is often used in hubbed networks as well as in point-to-point network backbone situations.

 

DSP:  Digital Signal Processing - The concept of sampling analog waveforms in discrete time and manipulating these samples using algorithms which would be difficult or impossible in the analog domain

 

DST: Ampex automated library archive system for broadcast video server applications.  DST Systems include tape drives and robotic libraries designed to provide near on-line storage for video servers.

 

DSU/CSU:  Data Service Unit/Channel Service Unit - On some data networks, these are two separate devices.  On most networks used with the codec, this is a box which sits between the codec and the data circuit, used to interface and condition the data coming on and off the network.  This box may also contain diagnostic testing functions and indicators, and in the case of switched services, will perform all your dialing functions.  A DSU/CSU is required for all SW56 and DDS circuits, and is not included with your codec.

 

DTE/DCE:  Data Terminal Equipment/Data Computer Equipment - To avoid confusion, the data protocols mentioned above designate equipment and ports as either DTA or DCE.  In the case of the codec, the DSU/CSU or TA is ALWAYS the DCE and the codec is ALWAYS the DTE.  Plugging two DTEs together will not establish communication between them, since the DCE provides all the clocks required to run the data around.

 

DTF: Sony video tape product

 

DTMF:  Dual Tone Multi-Function

 

DUAL 56:  Two switched 56 calls made between videoconferencing equipment to allow data transfer at 112 kbit/s.  The videoconferencing equipment performs a two-channel inverse-multiplexing procedure to assure channel alignment.

 

DUPLEX:  On the plain old telephone system (POTS), the audio transmission can be considered "half duplex" since if both parties speak at the same time, their voices will intercept on the single pair of wires on each end of the call.  Most digital systems are duplex or "4 wire", allowing simultaneous and independent data (or encoded audio) to pass in each direction.  Some systems may be "simplex" which pass digits only in one direction.

 

DUPLEXER:  A device that combines transmit and receive signals on one antenna

 

DVA:  Wisconsin Department of Veterans Affairs

 

DVC - Digital Video Cassette: A digital tape recording format using approximately 5:1 compression to produce near‑Betacam quality on a very small cassette. Originated as a consumer product, but being used professionally as exemplified by Panasonic's variation, DVC‑Pro, and Sony's variation DVCam.

 

DVD - Digital Video Disk (or Digital Versatile Disk):   A new format for putting full length movies on a 5" CD using MPEG‑2 compression for "much better than VHS" quality.

 

DVE - Digital Video Effects: A "black box" which digitally manipulates the video to create special effects, for example, the ADO (Ampex Digital Optics) system. Common DVE effects include inverting the picture, shrinking it, moving it around within the frame of another picture, spinning it, and a great many more.

 

DYNAMIC ALLOCATION:  The ability to add or remove resources to/from a system based on actual need.  The alternative to dynamic allocation is to have a fixed amount of resources for a system, which are always dedicated to that system regardless of whether they are being used.

 

E1: A digital transmission link with a capacity of 2.048Mbit/s, used outside of North America.  Typically channelized into 30 DSOs, each capable of carrying a single voice conversation or data stream.  Uses two pairs of twisted pair wires.

 

E-911:  An enhanced emergency call service that enables the network to transmit the caller's location and other important information to public safety agencies

 

E-MAIL:  Electronic Mail - Networking systems that allow users to send and receive messages via computers and telephone modems.  Communication may be from within a building to international.

 

EARTH STATION:  Equipment on the earth that can transmit or receive satellite communications; in general usage, this term refers to receive‑only stations

 

EAS:  Extended Area Service - A local telephone service that offers customers an expanded toll-free calling area in exchange for a slightly higher basic service rate

 

EBBs:  Electronic Bulletin Boards - These are systems in which users can read and post short public messages or announcements stored on a central computer.  Messages are sent and received by users with microcomputers equipped with modems and communications software; the messages may be screened and posted within categories established by the system operator. 

 

ECB:  Wisconsin Educational Communications Board - A state agency charged with developing, operating and maintaining educational telecommunications in Wisconsin.  Services include Wisconsin Public Radio, Wisconsin Public Television, ITFS systems, School Radio Service, Learning Link, and a satellite uplink.  The ECB is governed by a board comprised of representatives from UW, VTAE, DPI, DOA, the Wisconsin State Legislature, various councils, and private citizens.

 

ECHO SUPPRESSION:  The insertion of mild attenuation in an acoustic echo canceler transmit and/or receive on the line (codec) side of the AEC which eliminates howling caused by excessive closed-loop gain and is useful to attenuate any residual echo signals

 

EDGE NUMBERS: Code numbers printed on the edge of 16 and 35mm motion picture film every foot which allow frames to be easily identified in an edit list.

 

EDUCATIONAL TELEVISION:  The use of television for classroom instruction and classroom enrichment programming, as well as community and cultural programming

 

EDL - Edit Decision List:  A list of edit decisions made during and edit session and usually saved to floppy disk. Allows an edit to be redone or modified at a later time without having to start all over again.

 

EEPROM:  Electrically Erasable Programmable Read-only Memory - A non-volatile, but electrically alterable, form of semiconductor storage.  These devices are present in some codecs, permitting long-term storage of codec configuration, dialing and related information for easy recall by the user.

 

EIA:  Electronic Industries Association - A standards organization specializing in the electrical and functional characteristics of interface equipment

 

EIRP:  Effective (or Equivalent) Isotropic Radiated Power - The transmitter's available power multiplied by the antenna's gain

 

EL/AZ:  El over Az - An antenna mount providing independent steering in azimuth and elevation

 

ELECTRONIC BULLETIN BOARD: See EBBs

 

ELECTRONIC CLASSROOM:  An instructional area which is characterized by the presence of two-way distance learning facilities such as receive video, 2-way audio, and possibly such advanced features as computer image reception/transmission, ability for sending/receiving data from a central site, etc.  Sometimes also referred to as in-house educational video equipment such as VCR's.

 

ELECTRONIC MAIL:  A system by which written messages are entered through a keyboard and distributed to individuals or groups subscribing to the service.  Messages are generally stored on a computer and forwarded to recipients when they request messages through the use of data terminal or other keyboard device.

 

ELEVATION ANGLE:  The vertical angle measured from the horizon up to a targeted satellite

 

EMI:  Electromagnetic Interference

 

EMBED: Placing a movie on a web page where it can be viewed without requiring a helper application.

 

ENCODE:  In the context of Indeo video, the process of converting the color space of a video clip from RGB to YUV and then compressing it.

 

ENCODER:  A signal scrambler

 

ENCRYPTION/DECRYPTION:  Special coding or scrambling of a communication signal for security purposes

 

END FINISH:  Quality of the surface at an optic-fiber's end, commonly described as mirror, mist, hackle, chipped, cracked or specified by final grit size used in polishing

 

END SEPARATION LOSS:  The optical power loss caused by distance between the end of a fiber and a source,detector, or another fiber.  See also:  Extrinsic joint loss

 

ENG:  Electronic News Gathering - A small format video unit often used by commercial news operations

 

EQUAL ACCESS:  The requirement that local phone companies offer all long-distance companies access to their network facilities that is equal in quality, type and price; describes the ability of customers to choose their own carrier for one-plus long-distance calling.

 

EQUILIBRIUM LENGTH:  For a specific excitation condition, the length of multimode optical waveguide necessary to attain stable distribution of power among propagating modes

 

EQUILIBRIUM MODE DISTRIBUTION:  The condition in a multimode optical fiber in which the relative power distribution among the propagating modes is independent of length.  Synonym:  Steady-state condition.  See also:  Equilibrium length, Mode; Mode coupling

 

ERVING:  Embarrass River Valley Instructional Network Group - A consortium of seven Waupaca and Shawano County school districts using fiber optics for distance education

 

ETHERNET:  Baseband protocol and technology developed by Xerox and widely supported by many manufacturers; a packet technology that operates at 10 Mbps over coaxial cable and allows terminals, concentrators, workstations, and hosts to communicate with each other

 

ETN:  Educational Telephone Network - A four‑wire dedicated telephone instructional system operated by Instructional Communications Systems (ICS), University of Wisconsin Extension.  CTNs, ETN and two‑wire telephones can be interconnected at ICS in Madison.

 

EXCHANGE:  The local area served by a central office or switching center.  An exchange can be identified by the area code and first three digits of a phone number.  Exchanges are grouped to form a Local Access and Transport Area.

 

EXTRINSIC JOINT LOSS:  Loss caused by imperfect alignment of fibers in a connector or splice.  Contributors include, angular misalignment, lateral offset, end separation, and end finish.  Generally synonymous with insertion loss.  See also:  Angular misalignment loss; End separation loss; intrinsic jointloss; Lateral offset loss

 

FAA:  Federal Aviation Administration

 

FACILITATOR:  The individual responsible for the local component at a distance education site who may or may not be an expert in the subject matter

 

FAST START: See progressive download.

 

FAX:  Facsimile Machine - Electronic technology that transmits documents, usually over telephone systems.  Facsimile devices are commonly referred to as FAX, telecopies or datafax.

 

FCC:  Federal Communications Commission - The federal agency responsible for regulating all use of the air waves for broadcast and electrical telecommunications purposes

 

FCC TYPE ACCEPTANCE:    A procedure of equipment certification ensuring compliance with FCC regulations - an FCC ID# is assigned

 

f/D:  Focal-length-to-Diameter ratio (of a reflector)

 

FEEDBACK:  (a) Video ‑ distortion of the picture caused when a video signal reenters the switcher and becomes overamplified; (b) Audio ‑ unpleasant howl from the speaker caused when the sound inadvertently is fed into the microphone and overamplified

 

FEEDHORN:  The focal point on an antenna (e.g. ITFS or satellite) that gathers the signal and sends it to the receive line

 

FEED SYSTEM:  The small, widebeam antenna that illuminates (gathers signal from) the reflector in an antenna system (convention speaks of illumination, even in a receive-only application, as if the antenna were transmitting)

 

FERRULE:  A component of a fiber-optic connection that holds a fiber in place and aids in its alignment

 

FIBER BANDWIDTH:  The frequency at which the magnitude of the fiber transfer function decreases to a specified fraction of the zero frequency value - often, the specified value is one-half the optical power at zero frequency

 

FIBER BUFFER:  Material used to protect an optical fiber or cable from physical damage, providing mechanical isolation or protection.  Fabrication techniques include both tight jacket, or loose tube, buffering, as well as multiple buffer layers.  See also:  Buffer; Fiber bundle

 

FIBER BUNDLE: An assembly of unbuffered optical fibers - Usually used as single transmission channel, as opposed to multifiber cables, which contain optically and mechanically isolated fibers, each of which provides a separate channel

 

FIBER-OPTIC LINK:  Any optical transmission channel designed to connect two end terminals or to be connected in series with other channels

 

FIBER OPTICS:  High capacity cable made of high-purity, hair-thin glass threads through which information (voice, video, data) is transmitted as pulsating light; the bandwidth capacity is much greater than conventional cable or copper wire.

 

FIBER RING:  A fiber-optic cable arrangement that sends every customer's data in two opposite directions toward another destination connected to the ring.  This redundancy guarantees that an accidental cut in the ring will not stop the customer's data from reaching its destination.  (See Redundancy, SONET)

 

FIELD:  One half of a video frame, consisting of every other row (scan line).

 

FILE FORMATS FOR VIDEO:  ASF, AVI, MP3, and MPEG file formats.

 

FIRMWARE:  Data and/or program software for the codec stored in a non-volatile form in a semiconductor memory circuit.  For codecs, the firmware is often housed in a plug-in module.

 

FIRST MILE CONNECTIONS:  Refers to the way in which programming is delivered from its source to a transmitter

 

FIRST NAME ANALYSIS:   A transparency technique wherein the first frame of the video file is a dummy frame that supplies the color or range of colors to be rendered as transparent:  the color of the chroma-key background, for example.  See transparency, transparency frame.

 

FLATTEN:  The process of converting a Macintosh file into a self-contained, single-forked file so that it is compatible with a Windows* environment.

 

FM:  Frequency Modulation - Encoding a carrier wave by variation of its frequency

 

FOB:  Freight on Board

 

FOC:  Fiber optic cable

 

FOCAL LENGTH:  The distance from the reflective surface of a parabolic antenna to the point at which incoming satellite signals are focused; the focal point

 

FOCAL POINT:  The point to which incoming satellite signals are focused from the reflective surface of a parabolic antenna

 

FOOTPRINT:  Coverage area of a satellite beam; a contour map showing EIRP, RFD, antenna size, or G/T contours within a satellite's coverage zone - different satellites have different footprints. Some footprints cover as much as one‑third of the earth

 

FOT:  Fiber optic terminal

 

FOTS:  Fiber Optics Transmission System - With little time delay, very low bit error rate, a superior method to transmit digital video signals

 

FOUR-WIRE TELEPHONE:  Dedicated telephone system that uses four wires (two to send and two to receive) and requires special telephone equipment - ETN and CTNs use this technology for interactive classes and meetings that link users over a wide area

 

FPS: An abbreviation for frames per second, a measure of frame rate.

 

FRACTIONAL T1:  Service offering data rates between 64 kbit/s (DSO rate) and 1.536 Mbit/s (DS1 rate), in specified intervals of 64 kbit/s

 

FRAME:  A segment of a digital signal that has a repetitive characteristic in that corresponding elements of successive frames represent the same things.  In a time-division multiplex system, a frame is a sequence of time slots, each containing a sample from one of the channels served by the multiplex system; the frame is repeated at the sampling rate, and each channel occupies the same sequence position in successive frames.

 

FRAME RATE:  Frequency in which video frames are displayed on a monitor, typically described in frames-per-second (fps).  Higher frame rates improve the appearance of vide motion.  Broadcast TV (full motion video) is 30 frames-per-second.

 

FRAME RELAY:  A form of packet switching, but using smaller packets and less error checking than traditional forms of packet switching (such as X.25).  Now a new international standard for efficiently handling highspeed, bursty data over wide area networks.

 

FREQUENCY:  The number of cycles per second of a electromagnetic transmission, usually described in hertz; generally, high frequency transmissions can carry more information at greater speeds than low frequency transmissions

 

FREQUENCY STABILITY:  The variation in a carrier's frequency that occurs over a time period and or temperature range

 

FRESNEL REFLECTION:  Reflection of a portion of the light incident on a planar interface between two homogeneous media having different refractive indices.  Fresnel reflection occurs at the air-glass interfaces at entrance and exit ends of an optical fiber.  Resultant transmission losses (on the order of 4% per interface) can be virtually eliminated by use of antireflection coatings or index matching materials.

 

FRESNEL REFLECTION LOSS:  Reflection losses that are incurred at the interface between two media of different refractive index (such as between the fiber glass core and air)

 

FRESNEL ZONE:  With respect to an antenna radiating electromagnetic waves, this term refers to the volume of space within which physical obstructions or changes in the media supporting propagation will have a significant long-range effect upon the radiation pattern, or on the signal strength at the receiver

 

FULL DUPLEX:  The ability to transmit simultaneously in both directions.  A transmission system, together with its associated equipment, capable of simultaneously transmitting and receiving signals, as opposed to simplex (unidirectional) or half-duplex (one direction at a time) systems.

 

FULL-MOTION VIDEO:  Not compressed.  A standard video signal of 30 frames per second and 525 horizontal lines per frame, which is capable of complete action.  Level 3 Video utilizing 2 audio channels suitable for use in Distance Education credit courses employing rapid motion (i.e. Grass Valley "E Series" codec and associated equipment).

 

FULLY INTERACTIVE AUDIO/VIDEO:  Two or more video conferencing sites can interact with one another via audio and video signals; two sites may be fully interactive without necessarily being full-motion sites

 

G2:  RealPlayer file format

 

GaAsFET:  Gallium Arsenide Field Effect Transistor - extremely reliable, also known as "solid state"

 

GAIN:  A measure of the amount of signal level amplification of output to input power expressed in decibels

 

GANNT CHART:  Project management chart showing activities as a series of bar charts

 

GATEWAY:  Used to describe a device that acts to connect two or more dissimilar networks and makes possible communication between/among them

 

GBS:  Giga-bits per second - Defines a rate multiple at which data/information may be transferred across a communications line.  1 Gbs equals 1,000,000,000 bits per second, or approximately 125 million characters per second (assuming 8 bits per character).

 

GEOSTATIONARY ORBIT:  An orbit located 22,300 miles above the earth's equator.  In this orbit, a communications satellite rotates around the earth at the same speed the earth rotates so that the satellite appears to remain stationary when viewed from earth

 

GEOSYNCHRONOUS:  Satellite orbit having a period equal to that of the earth's rotation (need not imply geostationary)

 

GEN-LOCK:  The synchronization of a piece of video equipment with an external video signal - in videoconferencing systems, all cameras should be gen-locked together

 

GHz:  Gigahertz - Unit of frequency equal to one billion Hertz or one thousand megaHertz or cycles per second

 

GIGABYTE: 1 Billion bytes

 

GLOBAND:  The name given for a set of European network services which offer digital dial-up bandwidth on demand in 64 kbit/s increments, accessed from the customer premise over PRI lines - these services are offered under different names in each participating country

 

GRADED-INDEX FIBER:  An optical fiber with a refractive index that gets progressively lower away from the axis.  This characteristic causes the light rays to be continually refocused by refraction in the core.   Graded index fibers have higher bandwidth than step index fiber.

 

GRADES:  Green and Rock Area Distance Education System - An ITFS user group in Janesville area

 

GRAINY PICTURE:  A poor picture condition usually the result of weak signal strength and a uniform distribution of noise appearing as spots or streaks throughout the picture

 

G/T:  (G upon T) - Gain-to-noise-Temperature - Ratio of a receiving system; its sensitivity "Figure of Merit"

 

GVG:  Grass Valley Group, Inc.

 

H.221:  A CCITT standard describing a method in inverse multiplexing for videoconferencing terminals, to be used to Px64 videoconferencing

 

H.261:  CCITT codec recommendation regarding a video codec for A-V services at p x 64kb/s (p = any integer from 1 to 32); motion compensation and field sub-sampling (loop filter) are implementations optional in the standard

 

H.320:  A set of CCITT standards describing methods to allow videoconferencing terminals from different manufactures to interoperate

 

HALF DUPLEX:  A circuit that permits communications in both directions, but not simultaneously

 

HALF-TRANSPONDER:  A method of transmitting two TV signals through a single transponder, by reducing the deviation and power allocated to each.  Half-transponder TV carriers each operate typically 4 dB to 7 dB below single-carrier saturation power.

 

HARD COPY:  Information printed in permanent form

 

HARDWARE:  Electronic equipment such as: computers, satellite dishes, cameras

 

HARMONIC:  A multiple of a signal's frequency

 

HDTV - High Definition Television:   A TV format capable of displaying on a wider screen (16x9 as opposed to the conventional 40) and at higher resolution.

 

HEADEND:  The central transmission point for a CATV or MATV system from which programming is distributed to users

 

HERTZ:  A unit of frequency equal to one cycle per second (cps).  One kilohertz equals 1000 cps; one megahertz equals 1 million cps; one gigahertz equals 1 billion cps

 

HETERODYNE:  The conversion of a signal's frequency by mixing it with another signal

 

H0,ISDN H0:  An H channel made up of 6 B channels to create a 384 kbit/s ISDN channel

 

H10,ISDN H10:  An H channel made up of 23 B channels to create a 1472 kbit/s ISDN channel

 

H11,ISDN H11:  An H channel made up of 24 B channels to create a 1536 kbit/s ISDN channel

 

H12,ISDN H12:  An H Channel made up of 30 B channels to create a 1920 kbit/s ISDN channel

 

H CHANNEL:  A transmission channel, defined in the CCITT ISDN Standards, made up of multiple B channels.  Currently defined H channels include H0 (384 kbit/s), H10 (1.472 Mbit/s), H11 (1.536 Mbit/s), and H12 (1.920 Mbit/s).

 

HOP:  One leg of a microwave relay system (see microwave)

 

HORIZON-TO-HORIZON MOUNT:  A type of satellite dish mount that allows the dish to track the arc of satellites from east to west

 

HUB:  A point or piece of equipment where a branch of a multipoint network is connected.  In a telegraph network, signals appear as dc pulses at the hub.  A network may have a number of geographically distributed hubs or bridging points.

 

HYBRID CD-ROM:  A single disc containing files for both a Windows PC and a Macintosh.

 

HYBRID PRIVATE/PUBLIC NETWORKING:  The creation of a network using both private leased lines and public switched facilities (digital dial-up bandwidth).  The goals of combining both networking technologies are increased performance and flexibility at reduced cost.

 

HYBRID SYSTEM:  A system that combines two or more communication technologies

 

HYBRID WAVELET TRANSFORM:  A combination of wavelet and transform algorithms within the same compression technology.

 

HYDROXYL ION ABSORPTION:  Absorption of optical power in optical fiber due to hydroxyl (OH) ions.  This absorption has to be minimized for low fiber loss

 

I/O: Input/Output

 

IBIT:  Interim Board on Information Technology

 

ICPM:  Incidental Carrier Phase Modulation

 

IEC:  Inter Exchange Carrier - Common carrier providing communications channels between local telephone companies (LECs, or Local Exchange Carriers); also known as long distance carriers, such at AT&T, MCI, Sprint, Schneider Communications, etc.

 

IEEE:  Institute of Electrical & Electronics Engineers

 

IETF PROTOCOLS:  The Cisco IP/TV solution ensures consistent and time-dependent data delivery with RTP and RTCP, and VCR-like media controls with Real Time Streaming Protocols (RTSP).

 

IF:  Intermediate Frequency

 

IFL:  Inter-Facility Link - Anything from a cross-site transmission line to a complete data network

 

IHETS:  Indiana Higher Education Telecommunications System

 

IMA: An audio codec which compresses 16‑bit audio at a ratio of 4:1.

 

IMPEDANCE:  A complex number representing resistance and reactance

 

IN-BAND SIGNALING:  Signaling made up of tones of defined bits which pass within the data transmission stream.  Tones sent over digital circuits are encoded into digital PCM bursts and sent as digital data within the data channel.

 

INDEO VIDEO:  Intel’s series of compressor and decompressor technologies for digital video, capable of producing software-only video playback.

 

INDEX MATCHING MATERIAL: A material, often a liquid or cement, whose refractive index is nearly equal to the core index, used to reduce Fresnel reflections from an optical fiber's end face.  See also:  Fresnel reflection; Refractive index

 

INDEX OF REFRACTION:  The ratio of the velocity of light in a vacuum to the velocity of light in a given medium

 

INDEX PROFILE:  In a graded-index optical fiber, the refractive index as a function of radius

 

INFORMATION GATEWAY:  A telecommunications service that provides customers with a unified method of easy access to a number of different information service providers.  Without a gateway, a customer has to make separate calls and use a variety of procedures.

 

INFORMATION SERVICES:  Information content from a supplier that flows through telecommunications systems.  Usually refers to information that customers are willing to pay for, such as weather forecasts, consumer protection advice, or financial information.

 

INFRARED (IR):  The bank of electromagnetic wavelengths between the visible part of the spectrum (about 750 nm) and microwaves (about 30 pm)

 

INFRASTRUCTURE:  See Telecommunications Infrastructure

 

INJECTION LASER DIODE (ILD):  A solid state semiconductor device consisting of a least one p-n junction capable of emitting coherent, stimulated radiation under specified conditions

 

INSERTION LOSS:  Total optical power loss caused by insertion of an optical component such as a connector, splice, or coupler into a previously continuous path

 

INTEGRATED DETECTOR/PREAMPLIFIER:  A single chip which contains a detector and an amplifier which converts optical signals to usable electrical output

 

INTELLIGENT AGENT: This is software which does not yet exist; it would create and manage class and field-of-study profiles, conduct sophisticated program searches, and make recommendations to users who request age-appropriate programs or segments. This component represents the primary value-added service of the ECB.  This function cannot be done by any other existing agency.

 

INTELSAT:  International Telecommunication Satellite Organization

 

INTERACTIVE SERVICES:  Information services that let a customer make choices about which information is to be received next.  Shopping at home via an electronic catalog that displays on a computer screen, or searching for a particular magazine article that is contained in a computer file of thousands of magazine articles, are two examples of interactive services.

 

INTERFRAME COMPRESSION:  A form of compression in which the codec compresses the data within one frame relative to others.  These relative frames are called delta frames.

 

INTERLACE: A process in which the picture is split into two fields by sending all the odd numbered lines to field one and all the even numbered lines to field two. This was necessary when there was not enough bandwidth to send a complete frame fast enough to create a non‑flickering image.

 

INTERLATA:  Telecommunications between LATAs

 

INTRAFRAME COMPRESSION:  A form of compression in which the codec compresses the data within one frame relative only to itself.  Key frames are compressed with intraframe compression because they must reconstruct an entire image without reference to other frames.

 

INTRALATA:  Telecommunications within a single LATA

 

INTRANET: A large private network, usually found in a corporate or educational environment. Intranets are typically faster and more stable than external networks, such as the Internet.

 

INTRINSIC JOINT LOSS:  Loss caused by fiber-parameter (e.g., core dimensions, profile parameter) mismatches when two nonidentical fibers are joined.  See also;  Extrinsic joint loss; lateral offset loss

 

INVERSE MULTIPLEXING:  The creation of a single higher-speed data channel by combining and synchronizing two or more lower-speed data channels

 

IP MULTICASTING:  For schedules or live broadcasts, bandwidth-saving the Cisco IP Multicast permits single-sender and multiple-receiver program transmission.  Only one real-time stream of data is sent for each program, no matter how many people tune in.

 

ISDN:  Integrated Services Digital Network - The worldwide standard for digital telephony.  The network signalling and transmission concept in which its wide area transmission is configured with equipment and transmission methods which utilize standardized digital signalling methods and equipment to enable voice, data, and video information to be transferred between user resources simultaneously.

 

ISDEN MULTIRATE:  A network-based ISDN service which allows users' network access equipment to dial network channels of bandwidth in increments of 64 kbit/s, up to 1536 kbit/s.  Access to ISDN Multirate service is obtained over ISDN PRI lines.

 

ISO:  International Standards Organization

 

ISOTROPIC:  Same values when measured along all directions

 

IT:  Information Technologies

 

ITAB:  Information Technology Advisory Board

 

ITFS:  Instructional Television Fixed Service - A technology which transmits television signals using frequencies higher than commercial television (2500-2686 MHz band designated by the FCC for educational use only).  This technology requires special licensing from the FCC

 

ITS:  The International Teleproduction Society.

 

ITV:  Instructional Television

 

ITVA:  International TV Association

 

IXC:  Interexchange Carrier - (As opposed to LEC) - A telephone company authorized to provide long-distance communications, but not local telephone service.  Companies like AT&T, US Sprint and MCI are IXCs.

 

JACK:  A connecting device to which a wire(s) of a circuit may be attached and which is arranged for the insertion of a plug

 

JEDI:  Jefferson Dane Distance Education Consortia

 

JPEG:  Joint Photographic Experts Group - An ISO video compression standard for storage and transmission of a variety of graphics images (not only NTSC in origin); it may be used in conjunction with fully compliant CCITT codecs and includes lossy and lossless modes.  A standard for compressing still pictures and video images in a form suitable for frame‑by‑frame editing.

 

K-12:  Kindergarten through high school (i.e. a school teaching one or more grades in the range Kindergarten through twelfth grades)

 

Ka‑BAND:  A satellite band (30/20 Ghz) used for spot beam experiments

 

KEYFRAME: Used with delta frames in temporal compression. Keyframes contain the complete video image, while delta frames contain only the changes between keyframes.

 

KEYKODE: A machine‑readable code printed on the edge of motion picture film which allows the film edge numbers to be electronically read and inserted in to an edit list. Very useful for generating a negative cut list from a video off‑line EDL.

 

Kbs:  Kilobits Per Second - A rate at which data/information may be transferred across a communications line.  1 Kbs equals 1,000 bits per second, or approximately 125 characters per second (assuming 8 bits per character)

 

KHz:  Kilohertz - Refers to a unit of frequency equal to 1,000 Hertz

 

KLYSTRON:  High powered, very expensive tube used in TV transmitters

 

Ku‑BAND SATELLITE TRANSMISSION:  Refers to frequencies in the 11 to 14 GHz band.  This band is used by the new generation of communication satellites to send and receive signals by satellite.

 

LTC - Linear Time Code: Time code recorded on a linear analog track on a video tape. Also called Longitudinal Time Code.

 

LAMBERTIAN EMITTER (RADIATOR):  Has the characteristic that the energy emitted in any direction is proportional to cos_ where _ is the angle from the normal to the emitting surface.  Surface emitting LEDs are Lambertian emitters.

 

LAN:  Local Area Network - A user-owned, user-operated, high-volume data transmission facility connecting a number of communicating devices (computers, terminals, word processors, printers, mass storage units, etc.) within a single building or campus of buildings

 

LASER:  Light amplification by stimulated emission of radiation.  This highly-focused beam of light (or its device) is used in fiber optics and optical video disc

 

LASING THRESHOLD:  The lowest excitation level at which a laser's output is dominated by stimulated emission rather than spontaneous emission.  See also:  Laster; Spontaneous emission; Stimulated emission

 

LATERAL OFFSET LOSS:  An optical power loss caused by transverse or lateral deviation from optimum alignment of source to optical fiber, fiber-to-fiber, or fiber-to-detector

 

LAST MILE CONNECTIONS:  The means by which programming is delivered to its final receiver (e.g. local ITFS system delivery of satellite‑fed programming to home television sets)

 

LATA:  Local Access Transport Area - Local telephone serving areas in the US established to create boundaries that distinguish between local and long-distance service.  Calls between LATAs are switched by long-distance companies, while calls within a LATA are handled by local phone companies.  LATAs are further divided into areas called exchanges.

 

LAUNCH ANGLE:  Angle between the light ray and the optical axis of an optical fiber or fiber bundle.

 

LCD:  Liquid Crystal Display - A very low-power device capable of displaying characters, words and symbols, often built into a codec or room controller panel

 

LDC:  Long Distance Carrier.  See IEC

 

LEARNING LINK:  A computer bulletin board utilized for educational related services

 

LEASED LINES:  A circuit rented for exclusive use twenty-four hours a day, seven days a week from a telephone company; the connection exists between two predetermined points and cannot be switched to other locations

 

LEC:  Local Exchange Carrier - A telephone company authorized to provide local service but not interLATA long-distance communications (e.g. Wisconsin Bell and Ameritech)

 

LED:  Light Emitting Diode

 

Letterbox: Placing a wide screen image on a conventional TV by placing black bands at the top and bottom of the screen.

 

LEVEL 3 VIDEO:  Full motion video utilizing 2 audio channels suitable for use in Distance Education credit courses employing rapid motion (i.e. Grass Valley "E Series" codec and associated equipment)

 

LIGHT:  1) In a strict sense the visible spectrum, nominally covering the wavelength range of 400 nm - 750 nm.  2) In the laser and optical communication fields, the much broader portion of the electromagnetic spectrum that can be handled by the basic optical techniques used for the visible spectrum extending from the near-ultraviolet region of approximately 0.3pm, through the visible region and into the mid-infrared region to 30pm. See also:  Infrared (IR); Ultraviolet (UV)

 

LIGHT EMITTING DIODE (LED):  A semiconductor device which emits incoherent light from a p-n junction (when biased with an electrical current).  Light may exit from the junction strip edge or from its surface, depending on the device's structure.

 

LINE OF SIGHT:  Transmission path uninhibited by physical objects in the intervening terrain, ultimately limited by the curvature of the earth

 

LINEAR:  Output proportional to input without introduction of distortion

 

LIP SYNC:  The maintenance of sound (i.e. speech) exactly in step with movement in a visual image (i.e. faces).  Because the processing time for the video portion of the signal is about 100 times longer than the audio processing time, codecs usually incorporate adjustable audio delay circuitry to delay/equalize the two signals, or regain lip sync.

 

LNA:  Low Noise Amplifier - Refers to electronic equipment, used in conjunction with satellite reception, intended to amplify extremely weak satellite signals without introduction of noise

 

LNB:  Low Noise Block - Downconverter, usually at the focal point of a satellite antenna; converts satellite frequencies to receiver frequencies (a type of LNC)

 

LNC:  Local Node Control is part of the classroom equipment to interface with the GVG's network MASTER 110.

 

LNC:  Low Noise Converter - Equipment that combines an LNA and down converter in one package

 

LO:  Local Oscillator

 

LOAD:  Termination, usually the transmit antenna

 

LOAD BALANCING:  Directs user requests to the least-busy server within each server cluster, minimizing bandwidth consumption and maximizing performance and scalability.

                                                                                 

LOCAL AREA NETWORK:  A datacommunications network spanning a limited geographical area, usually within a single facility or campus.  It provides communications between computers and peripherals.

 

LOCAL DECODE:  A feature of Indeo video interactive allowing the playback application to tell the codec to decode only a rectangular subregion of the source video image:  the viewport.  See viewport.

 

LOCAL LOOPBACK:  Loopback performed between an application and network access equipment.  The signal is sent from the application to the network access equipment and back to the application without being sent out over the network.

 

LOOK-ANGLE:  The angle at which an antenna must be aimed in order to "see" (i.e., receive the signal from) a particular satellite;  also called the position angle

 

LOOPBACK:  Analog signals are easy to test.  One simply probes the point of interest with an oscilloscope and checks for the proper signal.  High speed digital signals complicate things because they can't be measured easily by traditional test equipment.  To make tests easier, many digital equipment comes with loopback capability.  Loopback diagnostics allow you to "instruct" a piece of equipment in your digital link to "echo" any information sent to it in the reverse direction.  When properly looped back, the codec should echo (from the receiver output) any audio sent into the transmitter.  By enabling loopback at different points on a network, the defective portion can more easily be determined.

 

LOSSLESS:  Negligible signal loss.  Compression algorithms where no data is lost. LOSSIess codecs include the Animation codec and the None codec

 

LOSSY:  Something that causes degradation of the signal - a lowering of the signal from the source to the end

 

LOSSY COMPRESSION:  Compression after which some portion of the original data cannot be recovered with decompression.  Such compression is still useful because the human eye is more sensitive to some kinds of information than others, and therefore does not necessarily notice the difference between the original and the decompressed image.  Cinepak and JPEG are lossy codecs.

 

LPTV:  Low Power Television - Stations which cover only 10 to 15 miles and are designed as "neighborhood" stations or ones that cater to a specific audience; LPTV is technically identical to television translators

 

LSBIC:  Lake Superior Broadcast Instruction Council - One of the RETAs serving schools in the Channels 8 and 36 (Park Falls) television viewing areas and headquartered in Ashland

 

LSU:  LAN Service Unit - See: Multiband LSU

 

LUMINANCE:  That portion of a composite video signal that represents the monochrome or brightness parts of the image

 

MACROBENDING:  In an optical fiber, all macroscopic deviations of the axis from a straight line; distinguished from microbending - See also:  Microbending loss

 

MACROBENDING LOSS:  Attenuation which occurs as the fiber bend radius is decreased (wavelength dependent)

 

MATERIAL DISPERSION:  Light impulse broadening caused by various wavelengths of light traveling at differing velocities through a fiber.  Material dispersion increases with the increasing spectral width of the source.

 

MATTE: A black & white high contrast image that suppresses or cuts a hole in the background picture to allow the picture the matte was made from to seamlessly fit in the hole.

 

MATV:  Master Antenna Television - An antenna system for a large number of TV sets such as a school, hotel or apartment building, where many sets receive a signal from one antenna

 

MAX:  Media Access Exchange -  See: Multiband MAX

 

MBS:  Megabits Per Second - Rate at which data/information may be transferred across a communications line; 1 Mbs equals 1,000,000 bits per second, or approximately 125,000 characters per second (assuming 8 bits per character)

 

MCI:  Media Control Interface:  Microsoft’s interface for controlling multimedia devices such as a CD-ROM player or a video playback application.

 

MCU:  Multipoint Control Unit

 

MDS:  Multipoint Distribution Service - One channel broadcast from one location to various point.  The commercial counterpart to ITFS, often referred to as "wireless cable" because it can be used to deliver pay television programming directly to homes.  MDS subscribers must install microwave antennas to receive program transmissions.

 

MEDIASTREAM: Pinnacle video server product series capable of over 1,000 hours of online storage

 

MEET-ME-BRIDGE:  A type of telephone bridge that provides dial-in conferencing - can be accessed directly by calling a certain telephone number

 

MEGABYTE: 1 million bytes.

 

MERIDIONAL RAY:  A ray that passes through the axis of a fiber while being internally reflected (in contrast with a skew ray) and is confined to a single plane

 

MHZ:  Megahertz - Refers to a frequency equal to one million Hertz, or cycles per second

 

MICROBEND EDGE:  Wavelength at which, given a particular stress level on the fiber, a sharp increase in attenuation will occur

 

MICROBENDING LOSS:  In an optical fiber, loss caused by sharp curvatures involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters.  Such bends may result from fiber coating, cabling, packaging, installation, etc.  Note:  Microbending can cause significant radiative losses and mode coupling.  See also:  Macrobending

 

MICROPROCESSOR:  The heart of the computer - a silicon chip that processes data and controls the computer's components

 

MICROWAVE:  Short electrical wavelengths, usually from 30 cm to 1 cm or 1,000 MHz to 30 GHz, used to transport audio, video and data signals point to point.  A single transmit and receive link can cover up to 40 miles and requires clear line of sight.  This is accomplished via a series of antennas, transmitters and reflectors on towers.  Voice, data, or video communications travels in a straight line from tower to tower, and can be made fully compatible with digital service.

 

MICROWAVE BAND:  The band of frequencies, 1,000 megahertz or greater, that uses very short waves; these bands are used primarily for point‑to‑point communications

 

MILWAUKEE PUBLIC SCHOOLS:  One of the RETAs serving the ITFS Channel 9 area in Milwaukee

 

MMDS:  Multichannel Multipoint Distribution Service - or MDS, Multipoint Distribution Service

 

MODE:  In any cavity or transmission line, one of those electromagnetic field distributions that satisfies Maxwell's equations and the boundary conditions.  The field pattern of a mode depends on the wavelength, refractive index, and cavity or waveguide geometry.

 

MODE COUPLING:  In a optical fiber, the exchange of power among modes.  The exchange of power may reach statistical equilibrium after propagation over a finite distance that is designated the equilibrium length.  See also:  Equilibrium length; Mode; Mode scrambler

 

MODE FIELD DIAMETER, 2W:  A functional representation of the energy carrying region of the fiber. (also referred to as spot size)

 

MODE FILTER:  A device to remove high order modes to simulate equilibrium mode distribution in a short length of optical fiber.  See also:  Equilibrium mode distribution

 

MODE HOPPING: The tendency of a laser to shift center wavelength during operation

 

MODE PARTITION NOISE (MPN):  Tendency of the laser to change relative energy densities in various modes

 

MODE SCRAMBLER:  A device for inducing mode coupling in a optical fiber

 

MODEM:  Modulator/Demodulator - An electronic device added to a computer for the purpose of converting digital information to travel over a telephone line.  Modems also make the reverse conversion of analog telephone signals into digital bits for use by the computer.  Modems are bandwidth rated in bits per second - common modem speeds are 2,400 and 9,600 bits per second.

 

MODIFIED CHEMICAL VAPOR DEPOSITION (MCVD) PROCESS:  A process for manufacturing high quality multimode and single mode fibers developed at Bell Laboratories and widely used by Western Electric and many other companies

 

MODULATION:  Intentional variation of a signal parameter. The process of encoding audio or video

signals to be moved to other frequencies in order to facilitate transmission

 

MODULATOR:  A device that transfer baseband video or audio to a carrier

 

MONITOR:  Generally a television display used specifically for the display of video information

 

MPEG:  Motion Picture Experts Group - An ISO motion video and audio compression standard providing lossy or lossless compression.  It is useful for playing back multi-media images from CD-ROM.  Applications also extend to broadcasting and videoconferencing.  MPEG 1 uses a data rate of 1.5 Mbps (Mega Bits per Second).  MPEG 2 supports higher quality with a data rate (also called bit rate) of from 2 to 10 Mpbs.  MPEG 2 is the format used for satellite broadcasting (DSS), digital terrestrial broadcasting, and DVD.

 

MSO:  Multiple System Operator - A cable company that owns several systems

 

MTS:  Multichannel Television Sound - A narrowcast technology.  In addition to providing stereo music, MTS provides another channel for data delivery, additional language services or supplementary instructional television services.  Viewers need special equipment to receive MTS.

 

MULDEM:  A piece of equipment which provides multiplexing and digital interface capability onto an optical (i.e. fiber optic) network

 

MULTIBAND:  Name of product family of network access equipment manufactured by Ascend Communications

 

MULTIBAND LSU:  LAN Service Unit - The Ascend Multiband LSU is a member of the Ascend Multiband product family.  It allows LAN bridges and routers to be interconnected, creating WANs, using a combination of dedicated leased circuits and digital dial-up circuits.  By creating such hybrid networks, users can match bandwidth to real-time traffic loads, saving money and maximizing performance.

 

MULTIBAND MAX:  Media Access Exchange - The Ascend Multiband MAX is a member of the Ascend Multiband product family.  It is a system-level network access unit, with a cage and backplane into which cards can be inserted to configure it for various requirements.  It supports up to 32 host ports and up to 8 Mbit/s to the network.  It can be used to support multiple applications as well as connect videoconference MCUs to the digital dial-up network.

 

MULTIBAND PLUS:  Ascend Multiband Plus is a member of the Ascend Multiband product family.  Like all members of the Multiband family, it provides application access to digital dial-up bandwidth on demand.  Supports up to 4 simultaneous applications (video, LAN, backup, imaging, etc) and up to 3 Mbit/s to the network.

 

MULTIBAND RPM:  Remote Port Module - The Ascend Multiband RPM is a member of the Ascend Multiband product family.  A device used to extend data, control, and management data ports from a Multiband to application equipment located elsewhere in a facility.  An RPM might be thought of as a sophisticated repeater, converting high-speed data a control signals for transmission using simple unshielded twisted pair wiring over extended distances (typically up to 3400 feet).

 

MULTIBAND VSU:  Video Service Unit - Member of the Ascend Multiband product family.  It allows video-conference users to initially purchase a VSU for use as a dual 56 (112 kbit/s) CSU/DSU, and then easily upgrade the VSU to a full-fledged 384 kbit/s inverse multiplexer at a later date as requirements dictate.  The upgrade process is performed by remotely downloading new software from Ascend Communications.

 

MULTIFIBER CABLE:  An optical cable that contains two or more fibers, each of which provides a separate information channel.  See also:  Fiber bundle; Optical cable assembly

 

MULTIMEDIA: a digital communication medium that is characterized by the juxtaposition of different media including graphics, audio, and video. 

 

MULTIMODE FIBER:  An optical fiber that supports many propagating modes at a given wavelength

 

MULTIMODE DISTORTION:  In a multimode optical fiber, that pulse distortion resulting from differential mode propagation rates

 

MULTIMODE LASER:  A laser with a multilongitudinal spectrum, i.e. it emits in many longitudinal modes

 

MULTIPLEX:  Process by which multiple signals are transmitted over a single channel

 

MULTIPLEXER (MUX):  Hardware that brings together several low-speed communications lines, transforms them into one high-speed channel, and reverses the operation at the other end.  A device used for division of a transmission facility into two or more subchannels , either by splitting the frequency band into a narrower bands or by allotting a common channel to several rent transmitting devices one at a time

 

MULTIPLEXING:  Process of combining a number of individual channels into a common frequency band or into a common bit stream for transmission.  The converse equipment or process for separating a multiplexed stream into individual channels is called demultiplexer.

 

MULTIPOINT:  A communications system which allows three or more sites to participate in the transmission

 

MUX:  Multiplex or Multiplexer - A device that combines the signals from several lower bandwidth lines onto a single high bandwidth line

 

NANO:  Prefix meaning one billionth (e.g., nanosecond)

 

NAPLPS:  North American Presentation Level Protocol Standard - Used for videotext, allows presentation of high quality graphics

 

NARROWBAND:  A low-capacity communications circuit/path.  It usually implies a speed of 56Kbps or less.  (Contrast with wideband and broadband).

 

NARROWCASTING:  As compared to "broadcasting"  ‑ television and radio designed to reach small, targeted audiences with an audio or video signal that is transmitted from a central point and can be received by persons around the transmitter using special radio and television equipment.  ITFS, cable television, fiber optics and satellite are examples of narrowcast technologies.

 

NATIVE RESOLUTION:  The resolution at which the video file was captured.

 

NETWORK:  A system of terminals, switches and connections (lines and radio channels) that communicates information among users amd capable of simultaneous transmission of a given program

 

NETWORKING:  The tying together of multiple sites for the reception and possible transmission of information.  Networks can be composed of various transmission media, including copper wire, terrestrial microwave, or coaxial.

 

NEWIST:  Northeastern Wisconsin In-School Telecommunications - One of the RETAs serving the Channels 20 and 38 areas headquartered in Green Bay

 

NEWTEC:  Northeast Wisconsin Telecommunications Education Consortium - A group of school districts using ITFS for distance education and staff development in the Green Bay area

 

NFAS:   Non Facilities-Associated Signaling - Allows a D-channel on one ISDN PRI to control channels located on other PRIs.

 

NIBS:  Northwest Instructional Broadcast Service - One of the RETAs serving schools in the Channels 20 and 28 areas headquartered in Elmwood

 

NODE:  A termination point for two or more communications links.  The node can serve as the control location for forwarding data among the elements of a network or multiple networks, as well as performing other networking and, in some cases, local processing functions.

 

NOISE EQUIVALENT POWER (NEP):  The rms value of optical power which is required to produce an rms signal-to-noise ration of 1; and indication of noise level which defines the minimum detectable signal level.

 

NOISE:  Noise is anything present between the codecs other than the binary signal being transmitted.   (a) Audio ‑ unwanted sound signals; (b) Video ‑ electronic interference, snow, sparklies.  Random electrical signal, generated by circuit components or by natural disturbances, that corrupt the data by introducing errors .

 

NOISE FIGURE:  Measurement of noise contribution of an amplifier relative to a noise-free amplifier at a reference temperature; usually expressed in dB.  The degradation in signal-to-noise ratio caused by receiving equipment.

 

NOISE TEMPERATURE:  Noise measurement of a system, as the absolute temperature of a resistive source delivering equal noise power; expressed in (degrees) Kelvin

 

NON-LINEAR EDITOR: An editing system based on storage of video and audio on computer disk, where the order or lengths of scenes can be changed without the necessity of re‑assembling or copying the program.

 

NOTS:  Network Overhead Transmission Service (1.544 Mbps)

 

NPR:  National Public Radio

 

NSF:  National Science Foundation

 

NSI:  Nielsen Station Index

 

NTIA:  National Telecommunications Information Agency, U.S. Department of Commerce

 

NTSC - National Television System Committee:  A standard for color broadcasting developed in the 1950's for use mainly in North America and some of South America.  Consists of 525 horizontal lines at a field rate of 60 fields per second. (Two fields equals one complete Frame). Only 486 of these lines are used for picture. The rest are used for sync and extra information such as VITC and Closed Captioning.

 

NTU:  National Technological University (Fort Collins, CO)

 

NUTN: