Index - A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A-Z
AAR - See Automatic Alternate Routing.
A & B LEADS - Designation of leads derived from the midpoints of the two pairs comprising a 4-wire circuit.
ABBREVIATED DIALING - Preprogramming of a caller's phone system or long distance company's switch to recognize a 2- to 4-digit number as an abbreviation for a frequently dialed phone number, and automatically dial the whole number. - Synonym: Speed Dialing. Know as Terminal Speed Calling in some LEC tariffs.
ABSOLUTE DELAY - The actual time taken for a signal to transit a telecommunications circuit from end to end; affected by the actual circuit length and the "propagation constants" of the type of medium in use.
ACCEPTANCE TEST - Test operation of a new or modified device or system before usage by customers; ascertaining performance is to specifications. FCC equivalent - "Proof of Performance Testing."
ACCESS CHARGE - Cost assessed to users for connection ability to the interexchange, interstate message toll telephone networks of IEC's by the user's LEC, to send and receive calls beyond the immediate local exchange area. May be per minute fees levied on long distance companies, Subscriber Line Charges (SLCs) levied directly on regular local lines, fixed monthly fees for special telco circuits (i.e. WAL, DAL, T-1), or Special Access Surcharge (SAS) on special access circuits.
ACCESS CODE - In PBXs, a digit or digits dialed prior to dialing an outside call (most typically "9", or a digit entered on a feature phone set to activate functions like Call Forwarding or Conference Add-on (most typically "*"or "#."
ACCESS LINE - A telephone circuit connecting a customer location to a public network switching center.
ACCESS METHOD - 1.) In data processing, the software environment encountered by data communications entering and leaving the machine, as in IBM's VTAM or TCAM; 2.) In LANs, the technique used to arbitrate use of the physical transmission medium, as in CSMA/CD or Token Passing.
ACCOUNT CODE - In PBXs, a code digit or digits a user must enter before or after a call is dialed, to establish accounting for the charges for the call. (Compare to "Authorization Code" as used in public networks.)
ACCOUNTING RATE - The charge per unit of traffic or usage, which can be a unit of time or transmission capacity or actual information volume between territories controlled by different telecommunications authorities; used to establish international tariffs.
ACOUSTIC COUPLER - Means of connecting external devices to a telephone handset avoiding direct electrical connection; most commonly used for low-speed data terminals.
ACF - Advanced Communications Function in IBM data networks; a series of software products providing sophisticated data networking functions.
ACK - The "acknowledge" character in many data codes; used most commonly for an affirmative response of correct receipt. (Compare to NACK).
ADAPTIVE EQUALIZATION - Equalization of received digital signals capable of adjustment during actual transmission.
ADAPTIVE ROUTING - In data networks, routing algorithms capable of adjusting message routes in response to changes in traffic patterns or transmission channel failures.
ADCCP - Advanced Data Communications Control Procedure, a bit-oriented data link protocol developed as an ANSI standard, adopted in whole or in part by various computer makers.
ADDRESS - 1.) In software, a location that can be specifically located in a program; 2.) In communications networks, the distinct identifier of a place, service or function to be reached.
ADPCM - Adaptive Differential Pulse Code Modulation; A digital encoding technique that transmits only the changed information between successive samples of the signal; reduces the number of bits per sample from 8 to 4, permitting doubling of transmission capacity of facilities; used primarily for international facilities; common carriers recommend data rates not exceeding 4800 bps on ADPCM facilities.
AGGREGATOR - A wholesale buyer of (typically) dial network capacity who acts as the billing and collection agent for a common carrier, without needing a switch or switches for access or billing of its clients; a relatively new approach as of late 1989.
AIOD - See "Automatic Identification of Outward Dialing."
AIRLINE MILEAGE - Calculated point-to-point mileage between two connected locations in a network.
ALARM DISPLAY - An indicator or set of indicators of the operational status of a system or device; in telecommunications, usually grouped into "Major Alarms" indicating an entire system down or affected, and "Minor Alarms" indicating an impairment to partial operation.
ALGORITHM - a prescribed set of steps for accomplishment of a function or task; equivalent to a mathematical solution.
ALL TRUNKS BUSY SIGNAL ( ATB ) - In North America, a single tone interrupted at 120 impulses per minute rate to indicate all lines or trunks in a routing group are busy, and no alternate route has been found. Internationally, any of several signals are recognized by the CCITT, most being variations on a steady tone.
ALTERNATE ROUTE - A secondary communications path used to reach a destination if the primary path is unavailable.
ALTERNATE USE - The ability to use communications transmission facilities for multiple applications - voice or data being the most common example.
ALTERNATE VOICE DATA ( AVD ) - A single transmission facility usable for either voice or data. Most commonly applied to transoceanic private line circuits.
AMBIENT NOISE - Constant noise present in all forms of telecommunications paths; a given that communications networks must perform with.
AMERICAN NATIONAL STANDARDS INSTITUTE ( ANSI ) - Official repository of standards for the United States of America. Compare: British Standards Institute (BSI) for the United Kingdom. Example: ASCII data communications code is ANSI C.64 and CCITT International Telegraph Alphabet Number 5, with only the smallest variation in a few definitions.
AMERICAN WIRE GAUGE ( AWG ) - Descriptive of the diameter of wire conductors, particularly in twisted pair cabling; has effect on the transmission capacity and distance a given wire can offer. Internationally, wire size is described in millimetric diameter, except in England, where the weight in pounds per mile is used.
AMPLIFIER ( REPEATER ) - Electronic device to boost the strength of a signal, usually analog when an "amplifier."
AMPLITUDE - Magnitude or size; voltage or power of an electronic signal.
AMPLITUDE MODULATION (AM) - Modifying a "carrier" signal by varying its instantaneous power to represent the information it carries; most commonly called "AM."
ANALOG LOOPBACK ( ALB ) - Connecting a received analog signal to the return transmitting path; a common test method for locating transmission problems in data transmission systems.
ANALOG SIGNAL - A signal in the form of a continuous varying in step with the actual transmitted information; attempts to transmit an exact replica of the inputted signal down a communications channel.
ANALOG TRANSMISSION - Communications by transmission of continuously varying representations of the input signal, as compared to coded words in digital transmission.
ANGLE MODULATION - Refers to the change of angle of a signal that occurs in Frequency Modulation or Phase Modulation communications systems; usually analog.
ANNUNCIATOR - (1) An audible intercept device that states the condition or restrictions associated with circuits or procedures. See also "Recorded Announcement Trunk." (2) - A buzzer, lamp, or other device to signal a line requiring operator attention on a switchboard.
ANSWER BACK - An electrical and/or visual indication to the call originating end that the call terminating end is on the line. First associated with the International Telex network, answerbacks are also recommended in CCITT- standard fax machines and are provided in most PC data communications software packages.
ANSWER SUPERVISION - An electrical signal fed in the reverse direction of a telephone circuit indicating the called location has responded to the connection request; starts billing of a call.
APPLICATION LAYER - The topmost, visible to the user, presentation of a communications network; the user interface point in network architectures.
ARC - "Attached Resource Computer," the root name of the LAN developed by Datapoint Corporation called "Arcnet" (which see elsewhere).
ARCNET - A LAN architecture developed by Datapoint Corporation featuring low cost for connection of groups of (Async) terminals to a (mini) computer within a premises.
AREA CODE - Colloquial term for a three digit number identifying one of more than 150 geographic areas of North America providing for Direct Distance Dialing on the public telephone network system. This entire system of numbers is under the umbrella of Country Code 01 in the World Numbering Plan of the CCITT. - Synonym: Numbering Plan Area (NPA).
ARQ - Telegraphic code signal for "Automatic Repeat Request," a time-honored method of telegraphic error correction upon which most data transmission error correction is based. ARQ receivers check for errors and initiate an order to retransmit data blocks determined to be corrupted in transmission.
ASCII - AMERICAN (NATIONAL) STANDARD CODE FOR INFORMATION INTERCHANGE; The most common code used for asynchronous data transmission by minicomputers and personal computers; derived from the TWX code of the Bell Model 28 teleprinter, expanded to use all possible character combinations; consists of 7 information bits with an 8th parity bit for error checking; numerous variations exist, for example use of the 8th bit in personal computers to extend the code with a number of graphics, special language characters and diacritical marks. Many common carrier data services cannot transmit the 8th bit needed to use that common PC extension of ASCII's alphabet.
ASR - Telegraphic name for an "Automatic Send/Receive" terminal station, typically one that has storage for outbound messages and holds them until called upon by the communications network to send. Compare to "KSR."
ASYNCHRONOUS - Occurring without central control or in an unpredictable time interval between successive elements; the typical mode of telegraphy, minicomputers and personal computers; requires s transmission of "start" and "stop" bits to provide decoding synchronization at the receiver.
ATTENDANT POSITION - A telephone switchboard operator's position. It provides either automatic (cordless) or manual (plug and jack) operator controls for incoming and/or outgoing telephone calls. Archaic: Turret.
ATTENUATION - Term denoting a decrease in power between that transmitted and that received due to loss through equipment, lines, or other transmission devices. Usually expressed as a ratio in dB (decibels). - Synonym: Loss; Antonym: Gain
AUDIBLE RINGING TONE - An audible signal heard by the calling party while a called station is being signaled of the call attempt. In North America, a unique signal of two tones on for two seconds and off for four seconds. Worldwide, variations abound in both tone character and interruption rate. - Synonym: Audible Ringback; Colloquialism: "Pacifier Ring."
AUTHORIZATION CODE - A 5 to 14-digit number entered on a dual-tone keypad that identifies the caller as a customer of the long distance service. Used primarily prior to Equal Access as a way to verify the caller and bill calls; continues today as a means to enter Calling Card numbers manually or from card readers on payphones. (Compare to "Accounting Code" in PBXs.)
AUTOMATIC ALTERNATE ROUTING (AAR) - Provision of function in a network to obtain a connection via secondary routes between two locations without need for user intervention.
AUTOMATIC ANSWER (AUTOANSWER; AUTO ANSWER) - A function providing for a transmission control unit or station to automatically detect being called and respond to an inbound call. Most commonly associated with telephone answering sets, voice mail, automated attendants and data sets (modems) for computer terminals.
AUTOMATIC BAUD RATE DETECTION (AUTOBAUD) - A function of data TDM's (See "Time Division Multiplex") to sense and self-adjust to the data rate of connections made to one of the TDM's ports. Typically used when connecting a dial-up modem to a port of a remote TDM to provide data dial-in service at a distant location.
AUTOMATIC CALL DISTRIBUTOR (ACD) - Often abbreviated "ACD;" provided as a feature on a PBX or Centrex, or as a stand-alone unit on user premises to distribute large amounts of incoming calls to a group of attendants or agents on a controlled and managed basis. Many management options exist to control and oversee the flow of call traffic to the agents. A major tool of inbound telemarketing centers.
AUTOMATIC CALLING UNIT (ACU) - Often abbreviated "ACU;" devices that dial a telephone call automatically on receipt of a demand for a connection and desired network number information from a Data Terminal Equipment (DTE). Bell 801 and CCITT V.25 units are the generic domestic and international equivalents.
AUTOMATIC DATA SPEED IDENTIFICATION - A function of integrated voice/data PBX switching systems to permit data devices and terminals of various data speeds to be connected in the PBX. Typically identified as "data classes of service" to sense and accommodate the data speed of a calling data terminal in order to route data calls. Frequently associated with an "automatic modem select" function in "modem pooling" arrangements or with "format and protocol conversion" capability to provide internal data calls between dissimilar devices and terminals.
AUTOMATIC DIALING UNIT (AUTODIALER) - A device programmed with frequently called numbers. The caller presses one to three digits and the preprogrammed number is automatically dialed into the phone circuit.
AUTOMATIC EXCLUSION (PRIVACY) - A telephone terminal systems function in which the first station on a line prevents access by all others on that line; identified with "bridge lifters" in local wire telephone plant; can be duplicated in digital local exchanges with software.
AUTOMATIC IDENTIFICATION OF OUTWARD DIALING (AIOD) - The function in some centrex units providing an itemized breakdown of charges (including individual charges for toll calls) for calls made by each telephone extension. Equivalent to Call Detail Recording ( CDR ) in electronic PBXs.
AUTOMATIC NUMBER IDENTIFICATION (ANI) - On long distance calls, the process by which the local phone company passes a caller's local billing phone number to his/her long distance company when a "1+" or "10XXX" call is made. With ANI a caller's long distance carrier knows who (what phone number) to bill without requiring the caller to enter an Authorization Code to be identified and billed.
AUTOMATIC REDIAL (AUTOMATIC RECALL) - A terminal function capable of detecting a busy signal and redialing the call until a connection is obtained; often called "Demon Dialer" after a consumer unit made for telephones.
AUTOMATIC ROUTE OPTIMIZATION - 1.) Synonym for "Least Cost Routing" (which see elsewhere); 2.) In some systems, may denote added ability to adjust routing depending on traffic load or time of day.
AUTOMATIC RINGDOWN (ARD) - A dedicated circuit on which no dialing is needed; simply seizing one end starts ringing at the other. Colloquially called a " hotline ."
AUTOMATIC ROUTE SELECTION (ARS) - See: Least Cost Routing.
AUTOMATIC TRUNK - A dial connection whose destination is predetermined, thus a request for service (called a seizure) initiates dialing to the programmed destination.