Telecommunication Glossary – ISP

A

1+ – What we call an “outbound” long distance call as in when you dial it (one plus the area code and number)

10xxx – The generic representation for an “access code” that enables a call to be routed over a carrier that that line being used is not “PICed” to.

800 – What we call an “inbound” call that is free to the caller because the toll charge is reversed and appears on the bill of the “callee”.

abbreviated dialing – The ability of a telephone user to reach frequently called numbers by using less than seven digits. Synonym: Speed Dialing.

access  – (1) Point at which entry is gained into a circuit or a network. May be switched or dedicated. (2) Ability to obtain data from a storage device or peripheral. (3) Type of connection between CPE and network.

access charge  – A fee paid by long-distance carriers to local telephone companies for use of local facilities, and by telephone subscribers to obtain access to local networks.

access code  – Preliminary digits a user is required to dial to be connected to a particular trunk group, channel or line. (2) A short sequence of digits allowing a user to access a specific facility, service, feature or function of a telecommunications network or computer system (see also 10xxx).

access control  – (1) Action taken to permit ordinary use of the components of a communications system. (2) The tasks performed by hardware, software and administrative controls to monitor system operation, ensure data integrity, perform user identification, record system access and changes and grant users access.

access line  – A circuit between a subscriber and a switching center. Any line giving access to a larger system or network. Also, the private lines feeding a common control switching arrangement or enhanced private switched communications service switch from a PBX.

access method – (1) A technique for moving data, voice or video between main storage and input/output devices. (2) In local area networks, the technique and/or program code used to determine use of the communications medium by granting access selectively to individual stations.

access tandem -  The switching system that provides distribution for originating or terminating traffic between End Offices and the Interexchange Carrier’s Point-of-Termination. An Access Tandem is also used to distribute originating or terminating traffic between a CLEC end office and an intraLATA toll point or an Interexchange Carrier’s Point of Termination

account  – Within billing terminology, this represents a customer’s product or service location.

account code – Two-digit code associated with an authorization code, identifying the caller.

acknowledge character (ack) – A transmission control character transmitted as an affirmative response to a connecting station or to a sender. [May also be used as an accuracy control character.]

acoustic coupler  – A special type of modem that converts acoustic energy (sound waves) into electrical energy, allowing a standard telephone handset to be attached to a computer or data terminal for data transmission.

adaptive transform coding  – An audio coding algorithm.

address address – (1) In a communications network, the identifying designation of an entity that is physically and/or logically distinct. (2) The destination of a message. (3) In software, a location that can be specifically referred to in a program. It can refer to a storage location, a terminal, a peripheral device, a cursor location or any other unit or component in a computer network.

agent – A person or company that acts on behalf of another. Typically individuals or companies that market the services of a carrier or equipment provider as if they were an employee of the carrier or provider.

aggregator – An independent entity that brings several subscribers together to form a group that can obtain long-distance services at reduced rates. The Interexchange carrier bills subscribers. The aggregator only provides the initial plan set-up. airline mileage – Calculated point-to-point mileage between terminal facilities.

alarm – A visual or audio signal which signifies that an error has occurred or an abnormal condition exists.

algorithm – A prescribed set of well-defined rules for the solution of a problem in a finite number of steps. For example a full statement of an arithmetic procedure for evaluating sine x to a stated precision.

all trunks busy (ATB)  – A single tone interrupted at a 120 impulses per minute (ipm) rate to indicate all lines or trunks in a routing group are busy.

allocate  – To assign a resource for use in performing a specific task.

alpha test – The stage during the research and development of a new product during which a prototype of the system is operated to determine whether the system concept and design are functional. Stage to identify areas that need further development and/or enhancement.

alpha-geometric – A high resolution videotex display technique. [Pictures are created by instructions such as draw a line, draw a circle, fill in an area. Picture definition is dependent upon the resolution capability of the display terminal.]

alpha-mosaic – A low resolution block-oriented videotex display technique. Picture definition is fixed at 64 by 60 elements, or pixels, no matter what the resolution capability of the display terminal.

alternate Access – A form of local access where the provider is not the local exchange carrier, but a company authorized to provide local access.

alternate route – A secondary communications path used to reach a destination if the primary path is unavailable.

alternate voice data (AVD) – A single transmission facility which can be used for either voice or data.

American Standard Code for Information Interchange (ACSII) – A code with seven information signals plus one parity check signal, designed for interworking between computers (i.e., the transmittal of text). The most popular coding method used by computers for converting letters, numbers, punctuation and control codes with digital form.

amplifier – (1) Device which receives an input signal in wave form and outputs a magnified signal. (2) Electronic device used to increase signal power or amplitude.

analog – A transmission method employing a continuous (rather than pulsed or digital) electrical signal that varies in amplitude or frequency in response to changes of sound, light, position, etc., imposed on a transducer in the sending device; opposite of digital.

analog signal – A signal in the form of a continuous varying physical quantity such as voltage -which reflects variations in some quantity; or loudness in the human voice as opposed to digital.

answerback – A signal sent by a data receiver to a data transmitter indicating it is ready to receive data, or is acknowledging the receipt of data. [The answerback is typically part of the "handshaking" between devices.]

answer supervision – (1) An off-hook signal indicating when the called party answers; used to read calls for billing purposes. (2) A signal generated by the originating switch (hardware answer supervision) or by the switch which terminates the call (software answer supervision, when FGA or WATS is used to terminate the call).

append – To change or alter a file or program.

application layer – The top layer of the OSI seven-layer logical structure for data services; the end-user layer.

applications software – The instructions that direct the hardware to perform specific functions. Common software applications include payroll, inventory control and electronic spreadsheets.

architecture – The interaction between hardware and software in a computing system to achieve the most economic, efficient, secure, rapid or low-maintenance system.

archive – A procedure for transferring information from an on-line storage diskette or memory area to an off-line storage medium.

area code – The three-digit numbering plan area code in North America which permits direct distance dialing on the telephone system. Synonym: Numbering Plan Area (NPA).

artificial intelligence – The capability of a computer to perform functions that are normally associated with human intelligence, such as reasoning, learning or self-improvement.

assembler – (1) A program capable of translating assembly code into digit code. The first major step in the automation of software development. Permitting symbolic (i.e., named) references to storage locations, rather than requiring the use of numbers, and eliminating the necessity to program in binary or other machine language. Synonym: assembly program.

assembly code – Programming language with statements that may be instructions or declarations. The instructions usually have a one-to-one correspondence with machine instructions.

assign – To give a new value to a variable during the running of a program.

asterisk laws – Gives consumers the right to say they don’t want to receive marketing phone calls by choosing to have an asterisk next to their names in the telephone book. The asterisk means “no phone solicitations.”

asynchronous computer – A computer in which each operation starts as a result of a signal generated by the completion of the previous operation, or by the availability of the parts of the computer required by the next event or operation.

asynchronous transmission – (1) A mode of data communications transmission in which time intervals between transmitted characters may be of unequal length. (2) Transmission independently controlled by start and stop elements at the beginning and end of each character. Synonym: start-stop transmission.

attenuation – Reduction in power level due to line resistance, leakage or induction which results in the received signal being lower in volume than the original transmitted signal. [In optical fiber systems there are other causes of attenuation, such as absorption, scattering and losses into radiation modes. It is usually expressed in decibel (dB).]

audible ringing tone – The information tone sent back to the calling party to indicate the called line is being rung.

audio response unit (ARU) – Output device which provides a spoken response to digital inquiries from a telephone or other device. The response is usually assembled by a computer from a prerecorded vocabulary of words.

authorization code – (1) Code that identifies the customer, and is used for billing purposes and validation by the switch. (2) An identification number that the customer enters when placing a call.

auto-dial – Automatic dialing; the capability of a terminal, modem, computer or a similar device to place a call and establish a connection over the switched telephone network without operator intervention.

automatic call distributor (ACD) – A switching system designed to queue and/or distribute a large volume of incoming calls to the next available “answering” position among a group of attendants.

automatic callback – A feature of a communications device or network that records, and can dial, the originating phone number of the last incoming call.

automatic dialing unit – A device which automatically generates a predetermined set of dialing digits when the corresponding button is pushed.

automatic message-switching center – In a communications network, location at which messages are automatically directed according to routing information within the message.

automatic number identification (ANI) – The number identifying equipment at local dial offices and sent to message accounting apparatus; the final four numbers of a seven-digit phone number.

automatic route selection (ARS) – Device (or software) which chooses the lowest cost route for long-distance calls over specific lines or services, including WATS, leased, specialized non-Bell common carriers (MCI, Sprint) or direct distance dialing (DDD). Synonym: Least Cost Routing.

auxiliary equipment – Equipment not under direct control of the central processing unit. Synonym: ancillary equipment.

availability – (1) The degree to which a system or resource is operable and not in a state of congestion or failure at any given point in time. (2) The percentage of total trunks in a group which can be accessed by a particular switch.

B

background bit error ratio (BBER) – (1) The ratio of the number of bits in error to the total number of bits received, exclusive of error bursts, over a special measurement period. (2) The error performance of the system under normal operation and does not include error bursts caused by line switching, maintenance, activity, etc. [An end-to-end BBER is not specified for digital private line because of the varying error distribution of access connection.]

background errors – Errors that occur during the normal operation of the system. They generally occur one at a time or a few at a time.

backup – The provision, logical or physical, of facilities to speed the process of restart and recovery following failure. Facilities may include duplicated files of transactions, periodic dumping of core or backing storage contents, duplicated processors, storage devices, terminals, telecommunications hardware or the switches to effect a changeover.

band – (1) The range of frequencies between two defined limits.

bandwidth – (1) The difference between the top and bottom limiting frequencies of a continuous frequency band. (2) Indicates the information-carrying capacity of a channel. Analog transmission usually expressed in kHz or MHz; digital transmission, bps, Mbps. Fiber-optic bandwidth is usually given as its capacity to transmit information in a specific time period for a specific length. (e.g. 10 Mbps/KM.) (3) Expressed in different measurements depending on transmission type.

bar-code scanner – (1) Optical character reader. A device used to read bar-codes by means of reflected light, such as the scanners that read the Universal Product Codes on supermarket products.

basic telecommunications access method (BTAM) – An access method that permits read/write communications with remote devices.

baud – (1) A unit of signaling speed. (2) A unit of data transmission speed measured in bits per second. [The speed in baud is the number of discreet conditions or signal elements per second. If each event represents only one bit condition, then baud is the same as bits per second.]

baud rate – A measure of signaling speed in data communications that specifies the maximum number of signal elements transmitted each second. [Over dial-up telephone lines, 300 and 1200 baud are most common. For most purposes, at slow speeds, a baud rate is the same as the speed in bits per second. Baud rate is the same as bit rate if all bits have the same length.]

Bell Operating Company (BOC) – Any of the 22 local Bell telephone companies owned by AT&T before divestiture. The independent BOCs provide primary access to the interexchange carriers. See RBOC.

BETA test – The stage at which a new product is tested under actual usage conditions. The purpose of beta testing is to locate and correct potential problems before consumer marketing begins. Follows Alpha Testing.

bid – (1) An attempt to gain control over a line in order to transmit data. (2) Usually associated with contention style of sharing a single line among several terminals. [Non-uniform time-outs at each terminal for reinstituting a bid if the line is busy give assurance that each terminal can have access to the line.

billed telephone number (BTN) - The "main number" of a customer's service that the LEC uses as a customer's account number. It is usually also an actual ANI. Will generally have WTNs associated with it. Every separate, distinct phone bill a customer gets will generally have a separate BTN.

billing cycle - A recurring period of time between traffic cut-off dates which precedes customer billing. Cycles are typically 30 days.

binary - A number system based upon twos rather than tens and that uses only two characters, zero (0) and one (1).

binary digit - Unit of information in two-level digital notation which may be 0 or 1. A member selected from a binary set.

binary synchronous transmission (BSC or bisync) - (1) Data transmission in which synchronization of characters is controlled by timing signals generated at the sending and receiving stations. (2) A half-duplex, character-oriented data communications protocol. Contrast with asynchronous transmission.

bipolar - Literally, having two poles. An input signal is bipolar when one electrical voltage polarity represents a logically true input and its opposite polarity represents a logically false input. Contrast with unipolar.

bit - (1) The smallest unit of coded information. (2) A pulse whose presence or absence indicates data. Abbreviation for binary digit.

bit duration - (1) Equivalent to the time that it takes one encoded bit to pass a point on the transmission medium. (2) In serial communications, a relative unit of time measurement used for comparison of delay times where the data rate of a transmission channel can vary (for example propagation delay, access latency).

bit rate - The rate at which bits (binary digits) are transmitted over a communications path. Normally expressed in bits per second (bps). [The bit rate is not to be confused with the data signaling rate which measures the rate of signal elements being transmitted.]

bit transfer rate – The number of bits transferred per unit time, usually expressed in bits per second (bps).

bit-oriented – Describes a communications protocol or transmission procedure where control information is encoded in fields of one or more bits; oriented toward full-duplex link operation.

bit map – A matrix of dots, all of the same density, that form an image.

bits per second (bps) – The rate at which data transmission (binary digits) is measured. See bit rate.

black box – A generic term used to identify functional equipment segments, as opposed to circuitry, that make up each segment of a telecommunications system.

block – A string of records, words or characters treated as a logical entity. Blocks are separated by interblock gaps, and each block may contain one or more records.

block error rate test (BLERT) – (1) In data communications testing, the ratio between the total number of blocks transmitted in a given message and the number of blocks in that message received in error. (2) A measure of the quality of a data transmission.

block length – A measure of the size of a block, usually specified in units such as records, words, computer words or characters.

blocked calls – All attempted calls that are not connected. Two most common reasons for non-connections: all lines to the central offices are in use; all connecting paths through the PBX/switch are in use.

blocking – (1) Engineering principle involving average time a user will wait while a call searches for the most economical route; opposed to queuing where a call waits for the most economical route. (2) Inability to establish a new call because of the inaccessibility of facilities in the system being called. Measured under grade of service using “P” factor.

Bell Operating Company (BOC) – Another name for the LEC, “baby bell” or local phone company.

bomb – To fail or crash.

booting – Technique for loading a program into a computer’s memory in which the program’s initial instructions direct the loading of the rest of the program. Usually, a few manual instructions must be entered on a keyboard, or a switch implemented to initiate the process.

bootstrap loader – An input routine in which simple preset computer operations are used to load instructions that in turn cause further instructions to be loaded until the complete computer program is in storage. [The term refers to the system "pulling itself up by its bootstraps."]

break – (1) To interrupt the sending of a message and take control of the circuit at the receiving end. (2) An interruption in continuity.

breakout box – A device that allows access to individual points on a physical interface connector for testing and monitoring.

breakout panel – A breakout box mounted as a component in some larger device.

bridge, bridging – Equipment and techniques used to match circuits to each other ensuring minimum transmission impairment. [Bridging is normally required on multipoint data channels were several local loops or channels are interconnected.

broadband - (1) A transmission facility having a bandwidth of greater than 20 kHz and, therefore, capable of higher-speed data transmission. (2) Analog transmission technique used with data and video transmissions that provides multiple channels for users through frequency division multiplexing.

broadcast - Transmission to a number of receiving locations simultaneously.

browser - Software used to access the web network, e.g., Netscape or Internet Explorer.

buffer - (1) A high-speed area of storage that is temporarily reserved for use in performing the input/output operation into which data is read or from which data is written. (2) Used to accumulate data into blocks of sufficient size to be handled efficiently by a processor or terminal. Synonym: I/O area.

bug - (1) A mistake or malfunction. (2) A program defect or error. [In 1946 Grace Hopper detected a problem with an Eniac computer at the University of Pennsylvania. Investigation uncovered an insect lodged within the computer causing the malfunction. Hopper's exclamation, "There's a bug in the computer," coined a new word for computer error.]

bulletin board – An electronic message center accessible through computer-aided communication lines.

burst – A sequence of signals in data communications counted as one unit in accordance with some specific criterion or measure.

burst errors – Bits or signals lost due to such problems as line switching or multiplex switching. [Typically involves a few thousand errors or lost bits at a time.]

bus – (1) A heavy conductor, or group of conductors, to which several units of the same type of equipment may be connected. (2) A path or channel for transmitting electrical signals and data, usually between a computer and peripheral equipment.

busy – Call condition in which transmission facilities are already in use. Synonym: off-hook condition.

busy hour – (1) The peak 60 minutes during a business day when the largest volume of communications traffic is handled. (2) When phone lines are most in demand and/or most used.

busy tone – A single tone that is interrupted at 60 ipm (impulses per minute) rate to indicate that the call’s terminating location is already in use.

bypass – When a customer avoids using the LEC to connect to their long distance carrier

byte – (1) The representation of a character. (2) A group of eight bits makes a byte. Typically a 16-bit “word” is itself divided into two bytes for handling. (3) Unit of measurement used to rate storage capacity of disks; usually the smallest addressable unit of information in a data store or memory. One thousand bytes is a kilobyte; one million bytes is a megabyte.

C

C band – A portion of the electromagnetic spectrum used heavily for satellite and microwave transmission; frequencies of approximately 4 to 6 GHz.

cache memory – A high-speed, buffer-type memory filled at medium speed from the main memory. [Programs and instructions found in the cache memory can be operated at higher speeds without the necessity of loading another segment.]

call-by-call selection – The ability to switch calls to individual trunks, rather than trunk groups, and to transmit necessary information to the specific trunk-type necessary to complete the call.

call detail record (CDR) – Computer record containing data unique to a specific call. [This information is processed as a unit and contains such details as originating switch, terminating switch, call length and time of day.] (2) Processing of call-specific information — start time, elapsed time, number dialed, date, and other pertinent customer data

call forward/with reason display – Enables the called number, during an internodal call, to forward the incoming call to an alternate destination and provide a message explaining why the call is being forwarded.

calling name delivery – Provides the ability during call setup to deliver the name of the calling party from the originating to the terminating switch or the name of the connected party from the terminating to originating switch. camp (or camp-on) – A PBX feature where a telephone line is busy and the incoming call is placed in a waiting mode until the line is available, at which time the call is automatically put through.

canned program – A software program written to meet the expected customer needs of a certain application. Opposite of custom programs.

capability – Data processing equipment characteristic by which one machine may accept and process data without conversion or code modification.

carrier – (1) A company authorized by appropriate regulatory agencies to provide communications services. (2) A continuous frequency capable of being modulated or impressed with a second information carrying signal.

carrier modulation – A signal at some fixed amplitude and frequency which is combined with an information bearing signal in the modulation process to produce and output a signal suitable for transmission.

carrier system – A method for providing several communications channels over a single path. Accomplished by modulating the data, voice or video transmissions onto a higher frequency carrier wave, then recovering it at the receiving end through a process of demodulation (See Frequency Division Multiplexing.)

categories of service – Basic and enhanced, as defined by the Federal Communications Commission (FCC). [Basic service refers to transmission capacity for the movement of information; for example residential telephone service. Enhanced service combines basic service with computer processing; for example Electronic Yellow Pages.]

cathode ray tube (CRT) – A vacuum tube display in which a beam of electrons can be controlled to form alphanumeric characters or symbols on a luminescent screen, for example, by use of a dot matrix.

cellular mobile radio – A radio-based system providing exchange telephone service to a station located in an auto or other mobile vehicle or device (for example briefcase). [Radio circuits transmitted to/from a base radio station cover a specific geographical area. As the vehicle or device moves from one area to another, different base radio stations handle the call.]

central office (CO) – (1) Location of telephone switching equipment where customers’ lines are terminated and interconnected. (2) Switching center that provides local access to the public network. Sometimes referred to as: End Office, Local Dial Office, Wire Center or Switching Center.

CENTREX – A type of private branch exchange service where incoming calls may be dialed direct to extensions without operator assistance. Outgoing and intercom calls may be dialed by extension users.

CENTREX, CO – Arrangement in which the Local Exchange Company’s service-providing switch is located in its central office.

CENTREX, CU – Arrangement in which the PBX features are provided by a switching system located on the customer’s premises, but work under the control of, or in conjunction with, equipment located in a LEC central office.

channel – (1) The smallest subdivision of a transmission system by means of which a single type of communication service is provided, for example, a voice channel or a data channel. (2) A communications path via a carrier or microwave radio. (3) In data communications, a path for electrical transmission between two or more points. (4) Within a computer, the electronic paths along which data flows between the input-output units of a computer and the customer premises equipment (CPU). Synonym: circuit, facility, line, link or path.

channel bank – (1) A part of the carrier system that performs the first step of modulation. (2) A multiplexer that modulates a group of channels into a higher frequency band and, conversely, demultiplexes the higher frequency band into individual channels. It can break a signal into the equivalent of 24 analog voice grade and/or 56 Kbps digital channels.

channel – The maximum bit rate that can be handled by a channel.

channel mileage charge – Monthly leased rate for circuits between telephone company (telco) central offices.

channel service unit (CSU) – Premises equipment that complies with Bell Technical Publication 62411 in providing loopback, keep-alive signals, alarm and status conditions.

channel termination charge – Fee associated with a T1 for the circuits feeding into a telco central office.

channel, four-wire – A two-way circuit, each with backup, where the signals simultaneously follow separate and distinct paths in opposite directions in the transmission medium.

character – (1) Any alphabetical letter, digit or special symbol. (2) In data transmission, the representation of a letter number or symbol by a specific code made up of binary digits.

character-oriented – A communications protocol or transmission procedure that carries control information encoded in fields of one or more bytes.

chips – Miniaturized microprocessors built on a single piece of silicon. [Typically, less than 1/2-inch square, they contain all the essential elements of a central processor, including the control logic, instruction decoding and arithmetic processing circuitry. Microprocessor chips are combined with memory and I/O integrated circuit chips to form a microcomputer, which usually fill no more than a single printed circuit board.]

circuit – A path for the transmission of electromagnetic signals; includes all conditioning and signaling equipment. Synonym: facility.

circuit grade – (1) The information-carrying capability of a circuit, delineated in speed or signal type. (2) For data use, capability within certain speed ranges.

circuit switching – (1) A method of communications, where an electrical connection between calling and called stations is established on demand for exclusive use of the circuit until the connection is released. (2) A switching system that completes a dedicated transmission path from sender to receiver at the time of transmission. See also: packet switching, store and forward, message switching.

class of service (COS) – (1) Telephone service distinctions which include: rate differences between individual and party lines, flat rate and message rate, and restricted and extended area service. (2) A subgrouping of telephone customers or users for the sake of rate distinction or limitation of service.

clock – A repetitive signaling device used to control a synchronous computer.

cluster controller – A device that handles the remote communications processing for multiple terminals or workstations.

coaxial cable – Cable consisting of an outer conductor surrounding an inner conductor, separated from each other by insulating material. It can carry a much higher bandwidth than a wire pair.

CODEC – Equipment containing a coder plus a decoder. Used to convert analog signals to digital form for transmission over a digital medium and back again to the original analog form.

cold boot – (1) First software initialization of the computer. (2) Software loading and checking just after the computer has been turned on.

color graphics adapter (CGA) – Equipment which provides 200 vertical x 600 horizontal pixel resolution for digital (rather than analog) video signals.

column – Vertical arrangement of characters.

common carrier – Government-regulated, private company that furnishes the general public with telecommunications services and facilities; for example, a telephone or telegraph company.

common channel interoffice signaling (CCIS) – A method in which labeled messages convey signaling and call completion information over a single circuit, leaving other circuits free for voice, data or video transmissions. common control switching arrangement (CCSA) – Network service that directs inward and outward dialing typically with a seven-digit code. Originally designed as a feature for private networks. Now seen in virtual switched private line networks.

common control switching 7 (CCS7) – A digital communications channel dedicated for the processing of signaling and call setup information between processors in the switched network. (2) An international standard for network signaling via data links operating at 56 kbps.

common intermediate format (CIF) – The type of coded video frame transmitted when using CCITT recommendation H.261 coding methods. CIF is 30 frames per second, 325H x 288V pixels.

communication – Transmission of intelligence between two points (origin and reception) without alteration of sequence or structure of the information content. See also data communication.

Communications Satellite Corporation (COMSAT) – A United States company created by an act of Congress in 1962 to provide communications via satellites. COMSAT leases satellite circuits to many American companies and is active in international communications through partial ownership in the International Telecommunications Satellite Organization (INTELSAT) and the International Maritime Satellite Organization (INMARSAT).

communications terminal – Any device which generates or receives electrical or tone signals that can be transmitted over a communications channel.

component video signal – Transmission in which the red (R), green (G) and blue (B) picture components are present as individual bits of information. [Synchronization information may be included with the G signal or be separate.]

composite video signal – Transmission incorporating luminance, color and synchronizing information.

compression – Techniques to reduce the number of bits required to represent information in data transmission or storage, thereby conserving bandwidth and/or memory. (2) Application technique.

continuous presence – A video processing, transmission and display mode that involves combining parts of two separate video images for transmission in a single data stream.

CompuServe – An information retrieval service which operates primarily in a videotex-like mode but also allows for standardized time-sharing as well as bibliographic and numeric retrieval. See: videotex

computer – A device capable of solving problems or manipulating data by accepting data, performing prescribed operations on the data and supplying the results of these operations. Various types of computers are: analog computer, digital computer, calculator.

computer-aided design (CAD) – Automation of the performance of various operations according to graphic design specifications through the use of a special computer and peripherals.

computer-aided manufacturing (CAM) – Automation of the performance of various operations according to manufacturing specifications through the use of a special computer and peripherals.

computer-assisted instruction (CAI) – An application in which a stand-alone personal computer or system is used to teach. Applications usually involve a dialog between students and software programs which inform students of their mistakes in a real-time manner.

computer science – The study of computer hardware and software.

concatenation – (1) To unite in a series; to link together; to chain. (2) The linking of transmission channels (phone lines, coaxial cable, optical fiber) end-to-end.

conditioning – (1) To bring to a standard. (2) Addition of equipment to voice grade lines to provide for data transmissions at specified minimum values of line characteristics, in ranges from C1 to C4 (the best). [Common carriers often recommend no conditioning for lines transmitting at 1200 baud; C1 for 2400 baud, C2 for 4800 baud and C4 for speeds above 4800 baud.]

conference call – A connection established among three or more stations in such a manner that each of the stations is able to communicate with all the others.

configuration – The interconnection and programming of independent machines or equipment to operate as a system.

contention – Condition on a communications channel or in a peripheral device when two or more stations try to either transmit at the same time or access a resource simultaneously.

control unit (CU) – Central processor of a telephone switching device.

Consultative Committee on International Telegraph and Telephone (CCITT) Consultative Committee on International Telegraph and Telephone (CCITT) – An internationally recognized advisory group that recommends worldwide standards for common-carrier communications services.

conversational mode – Operation of a data processing system in which a sequence of alternating entries between a user and the system takes place in a manner comparable to a conversation between two persons.

counter – Device which tallies the number of occurrences of an event (example, a cash register) .

country code – A one-, two- or three-digit number used for international dialing. [The first digit is always the world-zone number. Subsequent digits further define the geographic area.]

crash – Breakdown resulting from either a software or hardware malfunction.

crosstalk – Transmission noise caused by energy “leaking” from one channel to another on the same facility. [In analog voice communications, crosstalk makes conversation on one circuit accidentally audible on another.]

current loop – Transmission technique that recognizes current flows, rather than voltage levels. [Traditionally used in teletypewriter networks, incorporating batteries as the transmission power source.]

cursor – Position indicator frequently employed in terminals or workstations to indicate where a character is to be corrected or data is to be entered.

customer information system (CIS) – The Telco database which holds customer information such as service and product orders, installation dates, features used or invoice history. This information is pulled by IPS and other billing systems.

customer owned and maintained (COAM) – User provided and serviced communications equipment and its associated wiring.

customer premises equipment (CPE) – All telecommunications equipment (except pay phones) and, usually, wiring that is located at the users building.

customer service – A department in an organization that provides outbound services such as: technical assistance, help lines, product or account information, location of dealers, emergency responses, service information or complaint handling.

cut – (1) Transfer of a service from one facility to another. (2) Process of moving from a test environment into full production. (3) Implementation of a system in a continuous, time bound manner.

cut through – Establish a complete path for signaling and/or audio communications.

cyclic redundancy check – Error detection technique. [Using a polynomial, a series of two eight-bit block check characters are generated that represent the entire block of data. The block check characters are incorporated into the transmission frame, then checked at the receiving end.]

 

D

D4 framing format – (1) Division of DS1-level circuit into 24 equal channels. [Each channel carrier digitizes voice and signaling information in eight-bit bytes. A D4 frame consists of 192 (8 X 24) information bits. In addition, to identify each of the 24 channels, a framing bit is added in the 193rd position. Each byte is updated 8,000 times per second. Thus, the transmission speed of a DS1 circuit is 1,544,000 Hz (193 X 8,000).] (2) Monitors the DS1 signals for either framing errors or bipolar violations (BPVs). BPVs are eliminated when the bit stream passes through interfaces such as a multiplexer, Automatic Protection Switch or the Digital Cross-Connect System (DCS). Since no end-to-end performance monitoring is available using BPVs, the line must be taken out of service to test for large errors.

daisy chain – Connection of multiple devices in a serial fashion. [An advantage of daisy chaining is a savings in transmission facilities. The disadvantage is that if a device malfunctions, all other devices daisy-chained behind it are disabled.]

data – (1) Units of information. (2) Any representation, such as characters or analog quantities, to which meaning is or may be assigned.

data above voice (DAV) – Transmission system which carries digital data on a portion of the microwave radio spectrum above the frequency used for voice transmission.

data access arrangement (DAA) – Communication equipment furnished by a common carrier that allows attachment of privately owned data transmission equipment (DTE) to the common carrier network.

data communications – (1) Transfer of information between a source and a destination via one or more data links, according to appropriate protocols. (2) Transmission and reception of data, often including operations such as coding, decoding and validation.

data conversion – Process of changing information from one form of representation to another.

data coupler – A device to connect customer-owned modems or data sets to the regular telephone network. It functions by limiting the power applied to the line and providing network control and signaling.

data encryption standard (DES) – A cryptographic algorithm designed by the National Bureau of Standards to encipher and decipher data using a 64-bit key.

data pbx – A digital switch that allows a user on an attached circuit to select from other circuits, usually one at a time and on a contention basis, for the purpose of establishing a through connection. [A data PBX is distinguished from a PBX in that only digital transmission, and not analog, is supported.]

database – An organized compilation of computerized bits. [Formalized rules exist for the establishment, control and access of a database.]

datalink control – Second layer in the International Standards Organization reference model for Open Systems Interconnection (OSI). Synonym: protocol.

Datapac Network – A common user, packet-switched data network provided by The Computer Communications Group of the Trans Canada Telephone System.

dataphone – (1) A generic term to describe a family of devices to facilitate data communication. (2) An AT&T designation for a service which provides data communication over telephone facilities.

dataphone digital service (DDS) – A communications service of the Bell System in which data is transmitted in digital rather than analog form, thus eliminating the need for modems. See acronym list for other uses of DDS.

data terminal equipment (DTE) – (1) Provides for the communications control function (protocol). (2) Any piece of equipment at which a communications path begins or ends.

deadlock – Unresolved contention for the use of a resource.

debug – Checking the logic of a program to isolate and eliminate the mistakes from a computer program or other software. Synonym: troubleshoot.

decibel (dB) – (1) A unit of measure represented as a ratio of two voltages, currents or powers. (2) Measurement of transmission loss or gain.

decision table – (1) A matrix of contingency plans with the actions to be taken. [Sometimes used in place of flowcharts for program documentation.]

dedicated access line (DAL) – A non-switched circuit or path connecting the customer’s telephone equipment to the Telco switch with no intermediate switching functions by the Local Exchange Company (LEC).

dedicated line – A permanently assigned path to specific data terminals which is not part of a switched network. Synonym: private line.

delay dial – A switching configuration whereby local equipment will wait until it receives the entire telephone number before seizing a circuit to transmit the call.

delay distortion – Noise or echo resulting from the non-uniform speeds of various signal components of transmissions through a transmission medium(s).

demarc – (Demarcation Point) The point, jack or cross connect panel, at which ownership or responsibility for operating and maintaining facilities passes from one party to another.

demodulation – Conversion of a signal from either digital or analog to its original form. Antonym: modulation.

denial – Call condition that occurs when no circuits are available and a busy tone is returned to the calling party. [This situation is distinctly different from delay in that denial is not time-related and can only be measured in terms of the percentage of calls denied.] See blocking.

deregulation – (1) A 1983 Federal Communications Committee ruling which freed the interexchange carriers from the need to file rate changes or seek authority from FCC to expand. AT&T was not deregulated because of its economic power and market dominance.

diagnostic – Means of detection, discovery and further isolation of an equipment malfunction or a processing error.

dial access – (1) Connection through the public switched telephone network. (2) Means of providing a terminal switched access to a service, network or computer.

dial exchange – An automated switching junction or central office. For example, a PBX permitting call placement by rotary or pushbutton dialing rather than by an operator.

dial level – The selection of stations or services associated with a PBX using a one- to four-digit code (for example, dialing nine for access to outside dial tone).

dial pulse – A short duration, direct-current signal produced by or simulated to emulate the opening and closing of contacts in a rotary telephone dial when dialing numbers. Dial pulses control the action of telephone switching equipment. Also called rotary dialing.

dial repeating tie trunk – A private line communications arrangement which links two or more points together and permits direct trunk to trunk connections without use of an attendant.

dial selective signaling – A multipoint network in which the called party is selected by a prearranged dialing code.

dial tone – An audible signal indicating that automatic switching equipment is ready to receive signals required for a connection.

dial-up – Use of a rotary or dual tone multi-frequency (DTMF) telephone to initiate a station-to-station telephone call over the public switched network.

dial-up line – (1) A communications circuit that is established by a switched circuit connection. (2) Any circuit available over the public switched network.

dialing plan – A description of the telephone number assignments for customer use on a telecommunications network.

digital multiplex system (DMS) – A means of utilizing technologies that provide digital switched service for voice and data transmission. [DMS is characterized by the use of pulse code modulation (PCM) and time division multiplexing (TDM) throughout the switched network. It allows the direct switching of PCM signals used in transmission systems without their conversion to analog format.]

digital signal (DS) – (1) A nominally discontinuous electrical signal that changes from one state to another in discreet steps. (2) A signal that is time-wise discontinuous (i.e., discreet) and can assume a limited set of values. Antonym: analog.

digital signal hierarchy – A series of standardized increments for multiplexing of digital channels in T-carriers an other types of carrier systems for digital transmissions. The North American DS hierarchy is structured differently in other global regions.

ds0 – Digital Signal level zero. One 64 kbps capacity path, equivalent to one voice (analog) circuit.

ds1 – Digital Signal level one. One 1.544 Mbps digital signal comprised of 24 voice grade lines, each with 64 Kbps capacity. (See T1)

ds1c – One 3.152 Mbps pipe, equivalent to 48 voice grade lines, each with 64 Kbps capacity.

ds1 drop and insert arrangement – DS0-level channels are connected to and terminated at intermediate points between the originating and terminating locations within a network.

ds1 fan-out arrangement – DS0-level circuits are routed to several different locations from the single DS1 termination.

ds1 private line – An 1.544 Mbps leased, owned or otherwise dedicated circuit available through the LECs interexchange carrier (POP-to-POP or interLATA) or alternate carriers.

ds2 – Digital signal level two. One 6.312 Mbps channel, equivalent to 96 voice grade lines, each with 64 Kbps capacity.

ds3 – Digital signal level three. One 44.736 Mbps channel, equivalent to 672 voice grade lines, each with 64 Kbps capacity.

ds4 – Digital signal level four. One 375.176 Mbps channel, equivalent to 4,032 voice grade lines, each with 64 Kbps capacity. Typically used in interoffice transmissions.

digital technology – Method of storing, processing and transmitting information through the use of electronic or optical pulses that represent binary digits or bits (0 and 1).

digital transmission system – A transmission system in which information is transmitted in a series of pulses, and in which the signal can be regenerated. See also pulse modulation and time division multiplexing.

digitizer – Device used to convert an image to a series of dots that can be read, stored and manipulated by the computer. [A digitizer often scans video input, while a scanner usually scans hard copy input.]

diode – A two-electrode electron tube or its semiconductor equivalent. [Usually employed as liquid crystal diodes (LCD) or light emitting diodes (LED) and are especially applicable to portable computers.]

direct call – A facility which avoids the use of address selection signals or typed dialing sequences. The network interprets the off-hook status or call request signal as an instruction to establish a connection with a single destination address previously designated by the user.

direct distance dialing (DDD) – A toll service that permits customers to place their own long distance calls without the aid of an operator.

direct inward dialing (DID) – A PBX or CENTREX feature in which incoming calls are completed to extensions without the assistance of an operator.

direct mail – Any type of advertisement, brochure or printed piece delivered to a targeted audience, usually through the postal service.

direct outward dialing – A PBX or CENTREX feature that allows a station user to gain access to the public switched network without the assistance of an operator.

direct response – Refers to direct mail and telemarketing campaigns.

discrete – Pertains to separate and distinct parts of data such as holes in a card or graphic characters.

discrete cosine transform – An audio coding algorithm.

disk – (1) A magnetic recording medium. (2) A magnetically coated platter that stores programs and data files. [The two main types of disks are hard disks and floppy disks.]

disk operating system (DOS) – The software that provides instructions for system hardware operation and data processing.

distortion – (1) Any change from the original wave form or signal. (2) Normally, non-predictable changes which interfere with interpretation of the result.

distributed data processing (DDP) – Use of computer systems or intelligent terminals at multiple sites within an organization to perform data processing and/or storage functions.

distributed systems – Arrangements wherein an organization’s computer complex has many separate computing facilities interfaced and working in a cooperative manner.

down time – Period during which a computer, communications line or other device is not operating correctly because of mechanical or electronic failure. (As opposed to available time, idle time or stand-by time.)

download – (1) Transferring files from one computer to another. (2) Loading fonts from a computer to a printer.

downstream – The latter stages of processing in a computer program or system.

drop – (1) The portion of an outside telephone plant which extends from the telephone distribution cable to the subscriber’s premises. (2) A connection point for a terminal on a line.

dry circuit – A circuit which transmits voice signals and carries no direct current.

dual tone multifrequency (DTMF) – Type of signaling which emits two distinct frequencies for each indicated digit. Synonym: push button dialing, touch tone dialing

dumb terminal – (1) Conversational display terminal with limited resident intelligence. (2) Terminal capable of receiving and transmitting data from a host computer over a communications network.

duplex – (1) Two units in one. (2) Simultaneous two-way independent transmission. Synonym: full duplex.

E

E & M signaling – Method of receiving and transmitting signals. (Originally stood for ear and mouth).

External Binary Coded Decimal Interchange Code (EBCDIC) – A transmission system used by several IBM and IBM-compatible data terminals which consists of eight data bits, each of which represents a particular number, letter or character.

echo – A distortion that occurs when a signal is reflected or otherwise returned (on the same wire on which the speaker is speaking) with sufficient magnitude and delay as to be perceived by the speaker. [Typically, a problem on satellite circuits.]

echoplex – A method of checking and compensating for echos in network terminals that are operating in the two-way simultaneous mode.

edit – (1) To prepare data for a later operation. (2) Functions such as the rearrangement or the addition of data, the deletion of unwanted data, format control, code conversion and the application of standard processes such as zero suppression.

electronic key telephone set (EKTS) – Any key telephone with a built-in microprocessor which allows access to PBX-like features as well as access to multiple CO lines and uses two- to four-pair wiring.

electronic mail – (1) The electronic transmission of letters, messages and memos from one computer to another. (2) A computer-aided method of communication where an individual sends an on-line message to another individual via dial-up or dedicated access. See Bulletin Board.

electronic switching system (ESS) – Electronic versus electromechanical switching equipment.

electronic tandem network (ETN) – (1) A private network in which the network switch functions as a PBX and automatically connects the calling office to the called office through tandem-tie trunks.

email – Generic term for electronic mail.

emulate – (1) To imitate another system. (2) A method by which an imitating system can accept the same data, execute the same computer programs and achieve the same results as the original system.

enable – (1) To prepare a circuit for operation. (2) To allow an item to function.

encoding – (1) Inscribing or imprinting Magnetic Ink Character Recognition (MICR) characters on checks, deposits and other documents to be processed by a MICR reader. (2) The introduction of data on a medium such as a magnetic strip on plastic cards.

encryption – Conversion of data into code form for security purposes during transmission and decoding at the receiving end.

end office (EO) – A switching center where subscriber lines are terminated and where toll calls are switched through to the terminating destination.

enhanced services – Services using network facilities and computer processing that: act on the format, content, code, protocol or similar aspects of transmittal information; provide additional or restricted information or. involve subscriber interaction with stored data.

enterprise number – (1) A unique telephone exchange number that permits the terminating party to be automatically billed for incoming calls. (2) A toll-free

number.

equal access (EA) – (1) The concept — enforced by the 1984 Modified Final Judgement (MFJ) — that all Interexchange Carriers (IXC) must have the same access to the local BOC facilities as AT&T enjoys; provided as Feature Group D interconnection. (2) The arrangement whereby the BOCs provide trunk side connections to an End Office (EO), Automatic Number Identification (ANI), answer supervision, dial pulse or DTMF signal recognition.

equalization – (1) Procedure to compensate for fluctuation in circuit amplitude, delay or distortion and to produce a flat frequency response rate. (2) In data communications, a compensation for the increase of attenuation within frequency.

ergonomics – A discipline that promotes the consideration of human factors in the design of a working environment and its components (heat, light, sound, equipment).

erlang – (1) A unit of traffic intensity. (2) One erlang is the intensity at which one traffic path would be continually occupied.

error – (1) A difference between a computer value and the theoretically correct value. (2) A malfunction that is not reproducible. (3) In data communications, any unwanted change in the original contents of a transmission.

error burst – Results of an event that causes a lengthy stream of consecutively transmitted bits to be defective. [Retransmission is the normal correction procedure in the event of an error burst.]

error rate – Ratio of the number of signal elements (or data) incorrectly received to the total number transmitted. (2) The probability of an error occurring during the transmission of a message.

error-free seconds (EFS) – Ratio of the number of seconds in which there are no bits in error to the total number of seconds in the measurement interval.

errored second (ES) – A one-second interval containing one or more errors. [Its reciprocal, Error Free Second (EFS), is the more commonly used term.]

Ethernet – A packet-switched data local area network (LAN) design by Xerox Corp. which employs CSMA-CD as access control mechanism.

exchange (EX) – (1) A room or building equipped so that telephone lines terminating there may be interconnected as required. The equipment may include manual or automatic switching equipment. (2) A telephone switching center; an aggregate of traffic-carrying devices, switching stages, controlling and signaling means at a network node that enables subscriber lines and/or other telecommunication circuits to be interconnected as required by individual callers. (3) The territory served by an exchange, within which local service rates apply; also known as the exchange area or local service area.

expedite – The acceleration of a processing procedure, e.g., due date, that is different from the norm.

extended superframe format (ESF) – Use of the Cyclical Redundancy Check-6 (CRC-6) Code to measure actual logic errors rather than format errors. [ESF permits circuit performance to be measured in-service and real-time, regardless of the electrical/physical characteristics of the transmission facility and network. Error data processed and stored in the ESF CPU is available on demand for the last 24 hours in 15-minute intervals, making it possible to sectionalize problems.]

extract – A data synopsis from a given system which is passed to another system to complete processing.

 

F

facility – A transmission path between two or more locations without terminating or signaling equipment. [Addition of terminating equipment would produce either a channel, a central office line or a trunk. Various types of signaling would also be used depending on the application.}

facsimile – (1) A system for the transmission of a picture, drawing or other document by converting it into coded electrical signals which are subsequently converted into a replica of the original image at the receiving end. (2) The replicated image of picture, drawing or document. (See fax.)

facsimile transmission – An electronic means for transferring a document.

fault tolerance – The level of ability within a program or system to operate properly even if errors occur.

fax – (1) Abbreviation for facsimile. (2) Reference to either the service or the actual machines by which a copy of a document or picture may be transmitted

feature groups – The different types and qualities of public switched network connection between local telephone companies and long distance companies.

feature group A (FGA) – (1) A service that uses off-network access lines (ONAL). (2) A level of dial-up service in which subscribers have to dial a full local subscriber number to connect to the IXC, then have to key out (using DTMF) their personal authorization code followed by the distant number required.

feature group B (FGB) – (1) A dial-up service that gives no hardware answer code which means call timing may be inaccurate. (2) A service that uses off-network access trunks (ONAT) which eliminate most off-network access line difficulties and greatly improve transmission quality (for local offices).

feature group C (FGC) – (1) A dial-up service that uses off-network access trunks which eliminate most off-network access line difficulties and greatly improve transmission quality (for local tandem offices).

feature group D (FGD) – (1) A dial-up service employing a coding method to enable telephone customers to choose their long distance network and use the same number of digits whichever carrier chosen. (2) Uses off-network access trunks (ONAT). See Equal Access.

Federal Communications Commission (FCC) – Government agency established by the Communications Act of 1934 which regulates all interstate communications.

Federal Telecommunications System (FTS) – A government communications system administered by the General Services Administration (GSA), covering all 50 states plus Puerto Rico and the Virgin Islands; provides services for voice, teletypewriter, facsimile and data transmission.

feedback – (1) Return of part of the output of a machine, process or system to the computer as input for another phase; typically used for surveillance, self-correcting maintenance or control purposes. (2) Means of comparing or providing actual performance which can be compared with planned performance.

fiber optics – (1) A means of providing a high-speed transmission, using light to send images through a flexible bundle of glass fibers. (2) The use of light as the primary medium in an actual application.

fiber-optic transmission system (FOTS) – A means of sending data by coded light pulses through small diameter glass fibers. [Information is transferred by modulating the transmitted light. These modulated signals are detected by lig

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