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.