IT Glossary

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A 

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. 

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. 

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 - (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. 

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 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. [The first digit is never 1 or 0, and the second digit is always 1 or 0.] 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, leakages 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. 

autodial - 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. (2) In reference to WATS, one of the six specific geographic service areas as defined by Sprint. 

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 Sprint and other 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.]

billing contact - Departmental Staff who will receive billing information

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 or bandwith - 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.

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. [Normally associated with a multidrop line, where a number of terminals share the line]
buckets - (1) In Sprint billing software, an electronic file or folder in which records are kept until invoice processing occurs. (See Suspense File.) (2) In data, a storage unit. 

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.] 

building distribution frame (BDF) - The location in a building where equipment attaches a number of cables from the LDF's

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. 

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. [ISDN feature with Sprint.]

 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 -- to provide call detail reports and invoices. 

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. [ISDN feature with Sprint] 

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 capacity - 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. 

collision domain - In some network technologies, such as Ethernet, "collisions" of packets are possible. A collision domain is a group of machines on a network whose packets may collide with each other. Routers and switches break up collision domains and potentially increase performance.

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. Example: Signaling System 7. 

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. Synonym: Signaling System 7. 

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 outlet - The end location point for attachment of communication devices. It is typically a faceplate mounted on a wall with one or more jacks.

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.] 

conduit - Tubing, usually metal, through which cable is run, providing wiring for activation of voice and data lines. 

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) - 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.] 

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 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 team - A team of IT Communications Services staff who provide service to a particular U-M department. The team includes a CRM, Analyst, Engineer, etc.

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 Sprint switch with no intermediate switching functions by the Local Exchange Company (LEC). [Customers with DALs access the Sprint network directly and can use rotary or DTMF signals.] 

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). 

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 Commission ruling which freed Sprint and other 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. 

DHCP - Stands for "Dynamic Host Configuration Protocol". This protocol is based on BOOTP and BOOTP clients can still connect to a DHCP server. DHCP allows for dynamic allocation of network addresses and configurations to newly attached hosts, as well as recovery and reallocation of network addresses through a leasing mechanism. Rather than an administrator visiting each computer on a network and entering configuration data (IP address, default router, network mask, DNS server, NTP [Network Time Protocol] server, etc.), all computers are configured the same - to use DHCP. When the computers boot, they receive all of this configuration information from the DHCP server. If configuration information needs to change it can be edited in one place, the database, and each affected computer will receive the update. (For a DHCP FAQ see http://web.syr.edu/~jmwobus/comfaqs/dhcp.faq.html)

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 line/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. Sprint product: CLEARLINE 1.5 

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. 

DNS - Stands for "Domain Name System". This service maps an internet domain name to an IP address and visa versa. ITCom already runs a production DNS service. By integrating this service into this project a synergy can be achieved. Most DHCP/DNS systems require manual configuration of the associated data. This project plans to automate much of this process. A new computer is plugged into the network. The user authenticates and DHCP and DNS servers are automatically configured with the appropriate data. (For general DNS information see http://www.dms.csiro.au/~marka/dns.html)

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. 

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. 

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.

epitophier - A small piece of plastic located below each jack on a communications outlet. The color of the plastic indicates the type of service that may be provided on the jack.

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. [Customers may subscribe to the IXC of their choice.] 

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. 

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.
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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 precise reproduction. 

Family One Service - One of the new definitions of service level to be provided by IT Communications Services. ITD will provide a "quick response" to service requests in this category. This means the service will be provided right at the point of contact with ITD.

Family Two Service - One of the new definitions of service level to be provided by IT Communications Services. ITD will place service requests in this category on a "fastpath." This means the service will be provided within five days of the point of contact with ITD.

Family Three Service - One of the new definitions of service level to be provided by IT Communications Services. ITD will perform a "coordinated request" for service requests in this category. This means the service will require a number of ITD staff to be involved and it will take a greater amount of time to provide the service.

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. (3) A verb meaning to send an electronic image. 

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 light-sensitive semiconductor devices (photodiodes).] 

fiber-optic cable - A bundle of thin filaments of glass or other transparent materials used as the medium for transmitting coded light pulses that represent data, images or sound. 

fifo (first in-first out) queuing - Method where the next item to be retrieved is the item which has been waiting the longest. 

file - (1) An organized, named collection of records treated as a unit. (2) The storage media on which these records are kept. 

file server - A station or microprocessing computer dedicated to providing file and mass data storage services to the other stations on the local network. [Often found in Local Area Network (LAN) applications.] 

firmware - Computer programs that are embodied in a physical device that can form part of a machine. [Contrasted with software, which refers to the entire set of programs, procedures and documentation associated with a system, specifically computer programs, which are portable from one machine to another.] 

flat rate - (1) Fee for a product or service that is not dependent on usage. (2) Telephone tariff in which no charges are levied for local calls. (3) A rental charge which covers unlimited or equipment usage. 

flow control - The procedure for controlling the rate of transfer of packets between two designated points in a data network; used to prevent data loss during transmission. 

footprint - (1) That portion of the earth's surface illuminated by a narrow beam from a satellite. (2) Floor or work space occupied by a given unit of equipment. 

foreign exchange (FX) - A circuit that connects a subscriber in one exchange with a central office in another exchange. 

foreign exchange line - Line offered by a common carrier in which the user in one central office is assigned a telephone number belonging to a remote central office to minimize long distance charges. [Charges for these lines vary from carrier to carrier.]
forward channel - Communications path carrying voice or data from the originating caller to the terminating destination. 

forward error correction - Technique for regenerating lost data transmissions or errored messages; retransmission of any information by the transmitter. [Typically, this is accomplished by adding bits to each transmitted character or code clock using a predetermined algorithm. It doesn't need a feedback channel, and therefore may be used with a one-way transmission system.] 

frequency division multiplexing (FDM) - Method of transmitting two or more signals by dividing the available transmission frequency into narrower bands and using each as a separate channel. 

frequency modulation (FM) - Transmission method in which the frequency of the carrier wave is changed to correspond to changes in the signal wave.

full duplex - See duplex. 

G

G.711 - CCITT recommendation detailing a 74 kbps, 7-kHz bandwidth audio coding algorithm.

G.722 - CCITT recommendation detailing a 32 kbps, 3.4-kHz bandwidth audio coding algorithm. 

garbage - Unwanted or meaningless information being stored in a file or used in a process. 

gateway - Conceptual or logical network station that interconnects two otherwise incompatible networks, network nodes, subnetworks or devices. Gateways perform protocol-conversion operations across a wide spectrum of communications functions or layers. 

geosynchronous orbit - Position over the equator that communication satellites assume; an area about 23,000 miles above the earth's surface where a satellite's velocity matches the rotation of the earth, causing it to remain stationary relative to a point on the earth. 

gigabyte - One billion or one thousand million (109) bytes. 

garbage in-garbage out (GIGO) - Phrase used to describe quality of data input and output within a computer system; specifically, if input data is bad (garbage in) then the output data will also be bad (garbage out). 

glitch - A hardware malfunction. [As opposed to a software error, called a bug.] 

grade of service - (1) A measurement of the quality of telecommunications related to the availability of circuits when calls are to be made. Grade of service is based on the busiest hour of the day. It is measured in either percentage of calls blocked for dial-up access or average delay for manual situations. (2) The probability of a call being blocked by busy trunks; expressed as a decimal fraction. It usually pertains to the busy-hour probability. Referred to as the "P" factor. 

graphics - (1) Use of the computer for drawing lines under complete program control. (2) The on-line attachment of a vector scope and light pen to the computer, enabling the user and the computer to interact and jointly draw pictures on the face of the scope. 

H

H.221 - CCITT recommendation regarding frame structure for audiovisual teleservices. 

H.230 - CCITT recommendation regarding frame-synchronous control and indication signals for audiovisual systems. 

H.242 - CCITT recommendation regarding a system for establishing communication between audiovisual terminals using digital channels up to 2 Mbps. 

H.261 - CCITT recommendation regarding a video codec for audiovisual services. 

half duplex - Alternating the direction of transmission of signals between two terminals or computers but not transmitting in both directions simultaneously. Contrast with duplex. 

handoff - Process by which a cellular radio telephone call is transferred from one cell site to another. 

handset - That portion of the telephone containing the transmitter and receiver which is designed to be hand-held when the telephone is in use. 

handshake - A preliminary exchange of predetermined signals performed by modems and/or terminals and computers to verify that a communications link has been established and data transmission can proceed.

hardwire - To directly attach or dedicate a cable or line between units of equipment. 

hertz (Hz) - International standard unit of frequency. [Replaces, and is identical to, the older unit cycles-per-second.] 

heuristic - Pertaining to exploratory methods of problem solving in which solutions are arrived at by an interactive, self-learning method. 

hierarchical network - (1) A system, in which processing and control functions are performed at designated levels by computers specifically designed for those functions. (2) A switching architecture arranged in classes of offices with defined levels of responsibility. [Such as the American Class 1 to Class 5 network or the CCITT international network.] 
hierarchy - The relationship of various accounts or entities within a multi-level structure. 

hit-on-the-line - Description of the errors caused by external interferences such as impulse noise caused by lightning. 

holding time - The total period a communications channel or facility is in use for each transmission, including both message and operating times. 

homing - (1) Returning to the starting position, as in a rotary stepping switch. (2) Fixing a signal on the originating equipment to determine service quality or problems. 

hookswitch - The device on which the telephone receiver hangs or rests when not in use. 

housekeeping operation - The execution of a computer program that doesn't directly contribute to a product or service but is essential to the running of the system. For example, the initialization of storage areas or the execution of a calling sequence. Synonym: overhead operation. 

hubbing - Converting analog lines to a digital T1 facility. 

hunting - (1) Automatic routing of calls to an idle circuit in a prearranged group when the circuit called is busy. (2) The movement of a call as it progresses through a group of lines. [Typically, the call will try to be connected on the first line of the group; if that line is busy it will try the second line and then the third, etc.] 

I

in-band signaling,- (1) A type of transmission using an alternate current (AC) signal (usually 2,600 Hz) within the normal voice band. (2) An audible signal transmitted end-to-end on a long voice circuit without intermediate signaling equipment; requires that signaling equipment be arranged for "tone on when idle" operation.
inbound telemarketing - Any incoming sales or service function in an organization. [Inbound telemarketing is found in the following departments: customer service, order entry, reservation sales, technical hotlines or sales support.] 

infrared - Pertaining to the frequency range in the electromagnetic spectrum that is higher than radio frequencies but below the range of visible light. 

initialize - To set counters, switches, addresses or contents of storage to zero or another starting value at the beginning of or at prescribed points in the operation of a computer routine. 

input/output (I/O channel) - 1) A general term for equipment used to communicate with a computer. (2) The process of transmitting information from an external source to the computer, or from the computer to an external source. (3) Buffer area for the temporary storage of data. 

Installation Contact - Departmental Staff who will be responsible for the installation and may change the order even if there is a resulting change in price.

Integrated Services Digital Network (ISDN) - A switched network providing end-to-end digital connectivity for the simultaneous transmission of voice, data, video, imaging and fax over several multiplexed communications channels. Employs high-speed, out-of-band signaling protocols that conform to international standards. [Since signaling and communications are separate, the configuration reduces network blockage and provides faster connectivity for users.] 

interactive - (1) A conversational mode between a user and computer system. (2) Action in more than one direction, either simultaneously or sequentially. 

intercept - To stop a telephone call placed to an improper number and redirect that call to an operator or a recording. 
 

interconnect - (1) Arrangement that permits the connection of customers telecommunications equipment to a common carrier network. (2) Industry name for manufacturers, excluding AT&T and Bell companies, who provide telephone premises equipment. 

interexchange (IX) - Services or channels furnished between one or more rate centers or local and long distance carriers. 

interexchange carrier (IXC) - A provider of long distance service. 

interexchange plant - The facilities between the originating switching center and another switching center. 

interface - (1) A hardware and software link between two devices. (2) The junction or point of interconnection between two systems of equipment having different characteristics. For example, a computer card that allows users to transmit data using a variety of telecommunications modes. 

interference - (1) Unwanted noise, crosstalk or signal deviations on communications channels that result from natural or man-made occurrences. (2) Anything not properly a part of the signal or call being transmitted. 

interlata - Any connection or call that originates in one LATA and terminates in another.

intermachine trunk (IMT) - Circuit which connects two automatic switching centers.

internal line (non-DID line) - A non-direct-inward-dialed line on an electronic phone, commonly called a back-up or trunk hunting line, which parties outside the University cannot dial directly. These numbers are assigned as 2-xxxx (Ann Arbor), 5-xxxx(Dearborn) and 8-xxxx (Flint). Incoming calls are accepted on non-DID lines through a call hunt sequence when the primary number is already in use.

International Organization for Standardization (ISO) - An organization that promotes the development of standards to facilitate the international exchange of goods and services as well as develops mutual cooperation in areas of intellectual, scientific, technological and economic activity. 

International Record Carrier (IRC) - Exchange companies that offer telex and teletypewriter interconnect services. 

Internet Service Provider (ISP) - An entity that provides attachment to the Internet.

interoffice trunk (IOT) - A direct link between local exchange offices. 

interrupt - Stop a process in such a way that it can be resumed.

interstate - (1) Involving two or more states. (2) Any connection made between two states.

intraLATA - Any connection that originates and terminates within the boundaries of a single LATA.

intrastate - (1) Activity occuring within one state. (2) Any connection made that originates and terminates within the boundaries of a single state.

Invoice Processing System (IPS) - Sprint's integrated billing system for all customer bases.

ISDN - The Integrated Services Digital Network (ISDN) Dial-In Service operates like standard telephone service but is completely digital, allowing you to connect to the U-M campus network (UMnet) and the Internet from off campus at much higher speeds than with a regular analog modem.

IT Communications Engineer - ITD Staff who work with the department through the Network Analyst to design the services required by the customer. May be involved directly with the department on particularly complex installations.

IT Communications Installer - ITD Staff who install services at the department's site.

IT Communications Services - The ITD Staff who provide voice, video and data services to campus.

ITD Customer Relationship Manager (CRM) - ITD Staff who work with the department to determine what products and services are needed. The department's first contact within ITD.

J

jack - A connecting device having springs which make electrical contact with mating contacts of a plug. 

jitter - (1) A distortion caused by the variation of a signal from its references which can cause data transmission errors, particularly at high speeds. (2) Variations in amplitude, time, frequency or phase. 

Julian calendar - Calendar that is used in data processing. The dates are five-digit numbers: the first two digits pertain to the year and the last three to the day of the year (001 through 365 or 366).
jump scrolling - Vertical movement (up or down) of data lines, one line at a time, on a cathode ray tube (CRT). Contrast with smooth scrolling. 

justify - (1) To position characters of a text so that the left or right margins are aligned. (2) To order digits so that the least significant or most significant is always at the left or right margin.

K

K - (1) In the metric system, K means 1000. (Example: Km is 1000 meters). (2) In the computer industry, K means 210 or 1024 in decimal figures. 

key system - A telecommunications system with multi-button telephone sets on which more than one outside line terminates, allowing several people to answer or use more than one line. [All hardware is typically located on subscriber premises.] 

key telephone set - A multi-button phone used in a key system. 

kilo - (1) Greek word meaning 1000. (2) Prefix in the international system of measurements. (Example: kilohertz, kilowatts, etc.)

L

laser - A device which transmits an extremely narrow and coherent beam of electromagnetic energy in the visible light spectrum. [Acronym for Light Amplification by Stimulation of Emission of Radiation.] 

latency - Time interval between when a network station seeks access to a transmission channel and access is granted or received. 

layer - (1) Related processes, activities or information that constitute one level in a hierarchy or network platform. (2) Related communications-processing functions that comprise one level in a hierarchy of functions within the OSI reference model. 

learning curve - A planning technique calculation based on the premise that workers are able to produce any new product more quickly after they get used to making it. 

leased line - Any communication channel leased for exclusive use from a common carrier. Synonym: private line. 

least cost routing (LCR) - Method for automatic selection of the least costly facility for transmission of a call. Synonyms: Most Economical Route Selection (MERS); Route Optimization; Automatic Route Selection; Flexible Route Selection. 

level - (1) A group of related functions, activities or occurrences. (2) Expressed as the relative signal strength at a fixed point in a communications circuit . 

lightwave communications - The use of light as the primary medium in an actual application. [Lightwave communications is sometimes used in place of "optical" to avoid confusion with image transmissions such as facsimile or television.] See fiber optics. 

limited-distance modem - (1) A short-haul modem or line driver. [Since line conditions can be better controlled over short distances, some limited-distance modems operate at higher speeds than modems that are designed for use over analog telephone facilities.] 

line - Any communications path between two or more points, including satellite or microwave channels. See channel. 

line conditioning - Adjustment and control of the properties of a leased line to bring its characteristics within specified tariff limits; generally improves the frequency response and delay considerations of the line. [Line conditioning services provided by telephone carriers are designated as Type C or D (example C1, C2 or C4).] 

line driver - A modem alternative used when transmitting via Electronics Industry Association (EIA) cable over short distances, usually several hundred feet. (2) Device to amplify signals and reshape distorted pulses. 

line loading - Use of electrical components to improve the response characteristics of a communications line. 

line printer - (1) A device that prints a line of characters as a unit. (2) A line-at-a-time printer. 

line side - A circuit from a subscriber's telephone to the end or central office. 

link - A communications path between two nodes in a network. 

link layer - (1) The logical entity in the OSI model relative to transmission of data between adjacent network nodes. (2) The second processing level in the OSI model, between the physical and the network layers. 

loading - (1) Initializing software on a computer processing unit. (2) A means of adding regularly spaced inductance units on a circuit to improve its transmission characteristics. 

local access and transport area (LATA) - A geographical area designated by the FCC for the provision and administration of telephone service to individual customers; designated exchanges grouped to serve common social and economic communities of interest. 

Local Area Data (LAD) Circuit - One or more pairs of copper wire leased from a Regional Bell Operating Company (RBOC) which in Michigan's case is Ameritech. The quality of these wires is not guaranteed.

local area network (LAN) - An interconnecting multiple terminals, workstations, programs, storage and graphic devices within a relatively small geographic area. 

local distribution area (LDA) - An area that includes the rate centers (NXXs) served by an originating city.

local distribution frame(LDF) - One of the locations in a building where equipment attaches a number of cables for the communications outlets. Multiple LDFs are typically attached to one BDF.

local exchange carrier (LEC) - (1) Provider of local telephone service. (2) The provider of service within a LATA.

local loop - (1) The communications lines/services between the telephone subscriber and the LEC switching center. (2) The local connection between the end user and Class 5 central office or end office. 

loop - (1) A closed circuit. (2) The single connection from a switching center to an individual telecommunications instrument. 

loop back - A method of performing transmission tests on a circuit which does not require the assistance of personnel at the distant end. 

M

main distribution frame (MDF) - A steel bar framework that is the major cross connect point for COs and TOCs. Used to interconnect loop cable pairs and line equipment terminals on a switching system. Synonym: Main Frame. 

main pbx - A small, local telephone office or a device with the same functionality directly connected to a tandem switch via an access trunk group. 

mainframe - A central processing unit. 

manual tie line - A private communication channel which requires the assistance of an attendant at both ends of the circuit in order to complete a call. 

mapping - In network operations, the logical association of one set of values, such as addresses on one network, with other quantities or values, such as devices on a second network (for example name-address mapping, internetwork-route mapping). 
 

mark - (1) Symbol or symbols that indicate the beginning or the end of a field, word, item of data or sets of data such as a file, a record or a block. (2) To place a lead or ground on a terminal so that a hunting circuit may find that position and connect other equipment to it. (3) An indication, often in software, which shows the class of service to which a line is entitled, such as residential, business or public coin phone. 

mean time to repair (MTTR) - The average time required to restore a customer's service after a network failure. [In Sprint, this figure represents all failures due to either electronic components or fiber-optic cable malfunction POP-to-POP.] 

medium - [plural; media] (1) Material on which computer data is recorded, for example, magnetic tape, floppy diskette, winchester disk. (2) Any material substance that can be used for the propagation of signals from one point to another. (3) The communications forum chosen on marketing promotions and/or customer information. 

mega - (1) A Greek word meaning one million. (2) A prefix in the international system of measurements; for example: megabytes, that is one million bytes (106). 

megabyte - Literally 1,000,000 bytes; usually 1024 x 1024 bytes. 

megahertz (Mhz) - 1,000,000 (106) cycles per second. 

message - Complete transmission of data or text. Sometimes used interchangeably with block. 

Message Processing System (MPS) - Sprint system which prepares calls for invoicing. [MPS feeds to all billing systems as well as providing informational input on all billable and nonbillable traffic to network systems.] 

message telephone system (MTS) - (1) Generic name for the switched long distance service offered by all interexchange carriers. (2) An offering for which a charge is made in accordance with a measured amount of usage referred to as message units. Also referred to as Measured Telephone Service or Direct Distance Dialing (DDD). 

message unit (MU) - Standard against which charges for messages based on time and distance are measured. 

microwave - Any electromagnetic wave in the radio frequency spectrum above 890 megahertz. 

millisecond - One-thousandth of a second.

mode - (1) The most common or frequent value in a frequency distribution. (2) A particular form or variety of software. 

modem - [Contraction of Modulator-Demodulator.] A device which modulates and demodulates signals on a carrier frequency and allows the interface of digital terminals with analog carrier systems. [A modem is also known as a dataset.] 

modulation - Alterations in the characteristics of carrier waves, usually impressed on the amplitude and/or the frequency, for the purpose of transferring information. 

module - (1) A unit of something. (2) A unit of code performing a distinct function. 

monitoring device - Equipment which records data -- originating number, length, location -- on calls placed through a company telephone system. 

most economical route selection (MERS) - Method for automatic selection of the least costly facility for transmission of a call. Synonym: least cost routing 

mouse - Hand-held device which is moved around on a flat surface in order to position the cursor on a video display. 

multidrop line - Communications link with more than one terminal or station connected to it. 

multileaving - Transmission, usually via bisync facilities and protocols, of a variable number of datastreams between user devices and a computer. 

multiplex - (1) To interleave or simultaneously transmit two or more messages on a single channel. (2) A communications arrangement where multiple devices share a common transmission channel, though only one may transmit at a time. 

multiplexer - Hardware device that allows handling of multiple variable speed signals over a single, higher speed channel. 

multiplexing - Process or equipment that combines data from two or more individual circuits onto a higher speed circuit for transmission. [Two methods are used: (1) Frequency division where all channels are transmitted at the same time. (2) Time division where several messages timeshare a channel.] 

multipoint - (1) Line or channel connecting more than two different service points. (2) Circuit having points served by three or more switches. 

Multiple Appearance Directory Number (MADN) - allows the same directory number to appear on more than one telephone.

multitasking - System that can run two or more programs at the same time. [Apple's Multifinder, AT&T's UNIX and IBM's OS/2 are multitasking operating systems. By contrast, MS-DOS is a single-tasking operating system.] 

mux - [Abbreviation for multiplexing] The process or equipment for combining a number of paths into a single path or bit stream for transmission. 

N

nanosecond (NS, NSEC) - One-thousandth-millionth (or billionth) of a second. (10-9 second.)
network - (1) System of mutually-communicating devices (for example: computers, terminals, peripheral devices, process controllers) connected in common and for a purpose by one or more transmission facilities. (2) A collection of switches connected to one another by transmission facilities. 

Network Administrator - Departmental Staff member responsible for administering and maintaining a network.

network architecture - The philosophy and organizational concept for enabling communications between equipment at multiple locations; detailed specifications outlining the processors, terminals and transmission media, protocols and software to be used to accomplish accurate communications. 

network layer - The logical network entity that services the transport layer in the OSI model. It is responsible for ensuring that data passed to it from the transport layer is routed and delivered through the network. 

Network Operations Center (NOC) - The center responsible for monitoring network equipment. Usually a 24x365 operation.

network ring-again - A feature on a PBX that allows a caller, after encountering a busy signal, to be notified when the called line becomes free, provides the option of automatically reinstating the call. 

network topology - (1) Describes the physical and logical relationship of nodes in a network. (2) The schematic arrangement of the links and nodes of a network, typically either a star, ring, tree or bus topology, or some hybrid combination thereof. 

network trunks - Circuits connecting switching centers. 

network virtual terminal - A communications concept wherein a variety of DTEs, with different data rates, protocols, codes, and formats, are accommodated in the same network. This is done as a result of network processing, where each device's data is converted into a network standard format, then converted into the format of the receiving device at the destination end. 

nibble - Popular name for four bits, or half a byte. Also spelled nybble. 

node - (1) In network topology, a terminal of any branch of a network or a terminal common to two or more branches of a network. (2) In a switched network, the switching points, including patch and control facilities. (3) In a data network, the location of a data station which interconnects data transmission lines. (4) A point in a standing wave at which the amplitude is at a minimum. Synonyms: junction point, nodal point, vertex, null. 

noise - (1) Unplanned energy introduced onto a communications path, resulting in transmission errors. Undesirable signals bearing no desired information. (2) The unpredictable difference between the observed data and the true process.

non-blocking - A switching network having a sufficient number of paths such that an originating call can always reach any other idle station without encountering a busy signal. 

nonvolatile storage - A medium that maintains or keeps its contents when the power is removed. 

NNX (network numbering exchange) - Former three-digit location code which represented a central office. Now in NXX form, the available number of CO codes has been increased by permitting 0 and 1 as second digits in some circumstances. (See NXX.) 

NPA (numbering plan area) - A geographical boundary within which no two telephones will have the same seven-digit number. "N" is any number between two and nine, "P" is always one or zero; and "A" is any number excluding zero. (2) Area code. 

NXX (network numbering exchange) - An American Central Office Code where N is a digit 2 thru 9, and X is a digit 0 thru 9. Previously in NNX form, the available number of codes has now been increased by permitting 0 and 1 as second digits in some circumstances (previously their use was restricted to NPA codes). 

O

object program - (1) Fully compiled or assembled software that is ready to be loaded into the computer. (2) The output from processing a source program through an assembler or compiler. Synonym: object code. 

off-hook - (1) Condition existing when the receiver or handset is removed from its switchhook. (2) The active state (closed loop) of a single telephone or PBX line loop. 

off-line - (1) Condition that exists when devices or subsystems are not connected into, do not form a part of and/or are not subject to the same controls as an operational system. (2) A device which is not permanently connected to the processor or to external circuits. 

off-network access line (ONAL) - (1) A connection from a private switched network to the public switched network. 
(2) The connection provided by a carrier and used in common by subscribers to enter and/or exit from the switched network. 
(3) Circuit between Sprint switch and the line side of a telco office for FGA services. 

off-network access trunk (ONAT) - The circuit between the Sprint switch and the trunk side of a telco office for FGB and FGD services. 

off-network calling - Telephone calls which originate in or pass through private switching systems in transmission networks and are extended to stations in the public telephone system. 

off-premises extension (OPX) - Peripheral PBX equipment located in a building other than the one housing the PBX itself.
on hook - (1) Condition existing when the receiver or handset is resting on the switchhook. (2) The idle state (open loop) of a single telephone or PBX line loop. 

on network calling - A call that originates and terminates on a private network.

on-line system - A network interface which provides direct interface between applications programs stored in the computer and terminals used for data entry and output.

operating system - Software that controls the management and execution of programs.

operator assisted calls - (1) Direct distance dialing (DDD) calls which require and receive help by telephone company operators. (2) Person-to-person, collect calls, calling card calls from rotary phones, etc. 

optical fiber - Any filament or fiber made of dielectric materials that is used to transmit light and/or to guide signals. [Optical fiber typically consists of a core, that carries the signal and cladding, a substance with a slightly higher refractive index than the core, which surrounds the core and serves to reflect the light signal back into it.] 

original equipment manufacturer (OEM) - (1) Producer of a product made for assembly into a final system or larger subassembly by another. 

originating office - The central office that serves the calling party. 

other common carriers (OCC) - Specialized common carriers, domestic or international record carriers and domestic satellite carriers engaged in providing private line services (voice, data, audio or video) as authorized by the FCC. 

out-of-band - (1) Any entity outside an assigned range, scope or magnitude. (2) Any frequency outside the spectrum used for voice. 

out-of-band signaling - Use of a seperate data link which is not in the voice circuit to transmit call set-up and ANI information from carrier to carrier, or from carrier to customer.

outage - (1) Any disruption of service. (2) The point at which a customer releases a circuit for repair, lasting until the circuit is returned to the customer in working condition. 

outage time - Accumulated interval between unavailable and restoration time. It begins when a customer releases the circuit for repair and ends when the circuit is returned to the customer. 

outbound telemarketing - Any outgoing call designed to sell or service a customer or prospect. [Outbound telemarketing includes: lead generations, setting appointments, direct sales, collections and sales support.] 

overbuild - Adding radio capacity to a telecommunications network. 

overflow - (1) Switching equipment which operates when the traffic load exceeds the capacity of the regular equipment. (2) Traffic which is handled on overflow equipment. (3) Traffic which exceeds switching capacity and is lost. (4) The carry digit in a digital computer. (5) Intermediate message storage which serves as an extension of in-transit storage to preclude system saturation; an example, magnetic tape. 

P

P factor - Grade of service which describes the percentage of blocked calls. For example, P.10 means that 10 percent of all calls were blocked; P.01 means that 1 percent of all calls were blocked. 

packet assembler/disassembler (PAD) - (1) A non-adjustable resistance network used to insert transmission loss into a circuit. (2) To fill a block with dummy data, usually zeros or blanks.
PAD character - A fill character inserted when insufficient data characters are present to satisfy a field length requirement. 

parity - A constant state or equal value. 

parity bit - A check character or bit appended to an array of binary digits to make the sum of the digits, including the check bit, always odd or always even. 

parity checking - One of the oldest error checking techniques. Character bit patterns are forced into parity (total number of bits odd or even) by adding a 1 or 0 bit as appropriate, as they are transmitted. The parity (odd or even) is then verified upon receipt by the receiving device. 

patch - (1) To make an improvised modification (2) To change a software routine in a rough or expedient way. (3) A temporary electrical connection. 

PBX trunk - Connects a customer's PBX to another PBX, central office (CO), remote CO or Sprint switch. (See Private Branch exchange). 

percent denial - (1) A measure of the grade of service provided on a dial access circuit group; the average percentage of attempts blocked or denied due to a busy condition during the busy hour. 

peripheral - Any input/output device such as a printer or modem that is not a part of the main computer. 

personal identification number (PIN) - The last two digits of an authorization code that identify the caller. [The 14-digit number on a Sprint FONCARD that uniquely identifies the card holder.] 

phase jitter - A random distortion of signal lengths. [Phase jitter interferes with interpretation of information by changing the timing.]
phosphor - Material which coats the back side of a CRT screen. 

physical layer - Within the OSI model, lowest level of network processing below the link layer that is concerned with the electrical, mechanical and handshaking procedures over the interface that connects a device to a transmission medium (example, RS-232-C). 

picture element (pixel) - (1) A single dot on a computer display. (2) The smallest discrete part of a video image, the size of which is controlled by an analog-to-digital conversion sampling process. [The more picture elements per line, the higher the resolution of the image.] 

pixel - Single dot on a computer display, short for picture element. 

point-of-presence (POP) - The physical location within a LATA (local access and transport area) where an interexchange carrier's circuits connect with the lines of the local telephone company serving that LATA. 

point-to-point circuit - A private communications link between two terminations which does not connect with a public telephone system. 

polar keying - Technique of current loop signaling in which electrical flow direction establishes the two-level binary code. 

polling - Process by which a computer checks the readiness of other units to transmit or receive signals and information. 

port - (1) Entrance or access point to a computer, multiplexer network or device where signals may be supplied, extracted or observed. (2) The place where a peripheral device is connected to a computer. 

Postal, Telephone and Telegraph (PTT) - International administration, usually government controlled, which manages and operates postal and telecommunications services outside the country. Typically a monopoly operation. 

PostScript - Page-description programming language developed by Adobe Systems; designed to handle the placement of text and graphics on a page. The same PostScript file can be transmitted to printers of varying resolutions. 

presentation layer - The OSI processing layer that provides services to the application layer, allowing it to interpret the data exchanged as well as structure data messages to be transmitted in a specific display and control format. 

preventive maintenance - Precautionary measures taken on a system to forestall failures by providing for systematic inspection, detection and correction of incipient problems before they develop into major defects. 

Primary Directory Number(PDN) - your phone number. A PDN appears on the bottom button of an electronic phone, is the phone number assigned to a personal set. Dial 191 to determine the PDN if it is not marked.

primary routing point - The switch designated as the control point for a long-haul telephone call. 

private automatic branch exchange (PABX) - Small, local, automatic telephone office serving extensions in a business complex and providing access to the public network. 

private automatic exchange (PAX) - Small, local, automatic telephone office, normally serving extensions in a business complex, typically without external lines to the public network. 

private branch exchange (PBX) - Small, local, telephone office - either manually or automatically operated - serving extensions in a business complex and providing access to the public domain. 

private line - (1) A point-to-point telephone line for the exclusive use of one party. (2) A leased, owned or otherwise dedicated channel.
Private Line Service Center (PLSC) - Sprint organization which manages and maintains private line services. Each department is staffed with experienced professionals and subject matter experts in Private Line installation, service and support. 

private use network - Two or more channels contracted for by a customer and restricted for use by that customer only. 

program - A series of instructions or statements assembled in a form acceptable to a computer and prepared to achieve a certain result. 

prospect profile - A detailed description of a potential customer; the profile generally includes financial, demographic, industry, job title and past buying history information. 

protocol - A set of formalized conventions governing the format and relative timing of message exchange in a communications network. 

protocol conversion - Process of translating communications formats and timing, which would otherwise be incompatible, into messages understood by the network. Performed by a dedicated device, a software package loaded onto an existing system or by a value-added (intelligent) network. 

public service commission (PSC) - A regulatory authority at state level. 

public switched network (PSN) - Any switching system that provides a circuit switched to many customers. 

public utility commission (PUC) - A regulatory authority at state level. 

pulse - (1) A signal that can be wholly described by a constant amplitude and the duration time. (2) Signal form typically used internally in computers, terminals and other business machines as well as in communications facilities.
pulse code modulation (PCM) - Method of sampling information signals at regular intervals and transmitting the samples as a series of pulses in coded form which represent the amplitude of the information signal at that time. 

pulse modulation - Method of varying the amplitude, frequency or phrase of information-bearing signals into a series of pulses. [Typical methods involve modifying the amplitude (PAM), width or duration (PDM) or position (PPM). The most common pulse modu