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
BACKBONE FACILITIES - A transmission facility designed to interconnect tributary facilities from clusters of dispersed users or devices; viewpoint of what is a "backbone" can range from a single building's wiring to an intercontinental network.
BALUN - A form of impedance-matching transformer adapted by datacomm from radio antennas to connect unbalanced coaxially - interfaced data terminals to balanced twisted pair wiring in buildings.
BAND - (1) In analog transmission, the range of frequencies between two defined limits. - Synonym: Bandwidth . (2) In reference to WATS, one of five or more specific geographic areas as defined by the carrier.
BANDWIDTH - see BAND. BASEBAND 1.) In radio and analog communications. the total frequency band occupied by the aggregate of all the voice and data signals used to modulate a carrier. 2.) In LANs, a physical transmission path using direct digital signaling, usually at a rate stated in megabits per second.
BASIC TELECOMMUNICATIONS ACCESS METHOD (BTAM) - IBM's earliest I/O method for communications and computers; a series of macro - routines becoming extremely burdensome on the computer if more than about 15 remote terminals become active; replaced by VTAM at most users.
BATCH - 1.) In data processing, the processing of data accumulated over a period of time; 2.) In telecommunications, the accumulation of messages for transmission in a single group.
BAUD - A unit of signaling speed. The speed in Baud is the number of discrete conditions or signal elements per second. If each signal event represents only one bit condition, then Baud is the same as bits per second. Baud does not equal bits per second.
BELL OPERATING COMPANY (BOC) - Any of 22 LEC's spun off from AT&T as a result of the 1984 consent decree settlement; now grouped into 7 regional Bell holding companies (see also RBHC).
BINARY CODED DECIMAL (BCD) - A binary-coded notation in which each decimal digit of a number is expressed in binary form; Example: 23 decimal is 10111 in binary, and 0010 0011 in BCD.
BINARY CODED DECIMAL INTERCHANGE CODE (BCDIC) - IBM's earlier 7-bit implementation of a code for synchronous data communications. Virtually completely replaced by EBCDIC at this point in time.
BINARY SYNCHRONOUS COMMUNICATIONS (BISYNC, BSC) - IBM's half-duplex, character-oriented data protocol dating to 1964; more than 300 varieties of Bisync exist in IBM books alone with variations using BCDIC, EBCDIC, ASCII and Transcode and various error-checking schemes plus special characters as well as numerous non-IBM interpretations by other vendors. Still widely used as IBM attempts to unify all these in SDLC but most require extensive new hardware purchase.
BIPOLAR - 1.) In communications, the predominant line signaling method used for baseband digital transmission on local wire links for DDS and T-1; zero and one values are represented by positive and negative voltages respectively, as in " polar " telegraph circuits. Compare with AMI. 2.) In high-speed integrated circuit electronics, a similar technique used for transmission within a chip; typified by the name Bipolar CMOS .
BIT - The smallest unit of information in data processing; a contraction of the words," binary digit ."
BIT DURATION - The time taken for one bit to pass a point on a transmission link. Also called: bit length , bit time , bit interval , bit period , bit interval .
BIT ERROR RATE (BER) - The ratio between the number of bits transmitted and the number received in error on a transmission link; often used as a measure of quality for data links.
BIT ERROR RATE TEST (BERT) - Test method for digital links using a psuedorandom repeating sequence of (typically) 63, 511 or 2047 bits, comparing the received pattern with the known transmitted pattern for errors, computing the gross errors over a fixed test interval, typically 15 minutes. Error rate is stated in scientific notation as the number of errored bits per hundred thousand, million ten million or hundred million. Minimum acceptable error rate for voice channel data operations is one errored bit per 100,000 transmitted; computer users often find BERT testing insufficient for their needs. (see also BLERT ).
BIT ORIENTED - Descriptive of data communications protocols using a control byte rather than embedded control characters or control messages as well as having a high degree of transparency to codes used for messages. Typified by IBM's SDLC and the CCITT's HDLC of X.25 packet networks.
BITS PER SECOND (BPS) - basic unit of measurement for raw transmission throughput on a link. Often stated in kilobits , megabits , or gigabits .
BLOCK - In data communications, a string of data set into an "envelope" of synchronizing, addressing, control and error-checking characters transmitted as an entity. Synonomous with "packet" in X.25 packet networks. Equivalent to "frames" in digital communications systems.
BLOCK CHECK CHARACTER (BCC) - An error-checking character appended to a block of data representing the resulting parity check of all the characters in the block; associated technique known as Longitudinal Redundancy Check, or LRC .
BLOCK ERROR RATE (BLER) - The ratio of number of blocks transmitted to the number of blocks containing errors; a user-oriented measure of data transmission quality. Synonomous with "frame error rate" in digital communications line systems.
BLOCK ERROR RATE TEST (BLERT) - Data transmission testing in which the error rate counted is the number of blocks containing errored bits instead of the raw number of errored bits. Many users claim this is more representative of the real throughput quality of a circuit than simple raw BER testing.
BLOCK LENGTH - Measure of the size of a transmission block in data communications; stated in characters, records, language words, computer words, characters; but rarely bits.
BLOCKED CALLS (BLOCKING, CALL BLOCKING) - Attempted calls that are not connected because (1) all lines to the central offices are in use; or (2) all connecting paths through the PBX/switch are in use.
BOOTSTRAP LOADER - A computer input routine in which preset operations are placed into a computer that enable it to get into operation whenever a reset condition occurs; in electronic PBXs this may be called Automatic Program Loading or a similar term; in personal computers it is the sequence that searches predetermined disks for a Command Interpreter program, then a Configure System file; finally an Autoexecution Batch file.
BREAK - 1.) In the sense of a transmission impairment, a momentary interruption of a circuit. 2.) In data transmission systems, a timed interruption of about 300 milliseconds, often intended to interrupt a distant transmitting station.
BREAKEVEN POINT - Level of usage at which the total cost of a service with a high fixed up-front monthly fee but low minute costs becomes equal to the total cost of another service with low (or zero) monthly fee but relatively high per minute cost. At usage levels higher than breakeven, the service with the high monthly fee is cheaper.
BREAKOUT BOX - A very common and low-cost data interface test adapter permitting physical access to the interface pins to view the status; sometimes force conditions on some pins or even connect the pins differently. When mounted in a larger device, often called a breakout panel.
BRIDGE - 1.) In WANs, a device to connect transmission circuits in parallel; 2.) In LANs, an electronic device providing a logical connection path between two LAN physical segments.
BROADBAND - 1.) In analog transmission plant, a channel facility having a bandwidth of greater than nominal voice grade of about 3 khz. 2.) In LANs, an analog physical transport medium of very wide bandwidth, typically 300 megahertz or more.
BROADCAST - In telecommunications, a transmission mode in which every message is transmitted to all stations; only those authorized or ad or addressed will record, read or display it, however.
BUFFER - A temporary storage medium to permit some difference in the capacity of two data devices to emit and accept data from each other.
BUG - Computer term for an error or mistake causing a processing delay or stoppage.
BULLETIN BOARD SYSTEM (BBS, EBBS) - A communicating computer equipped so as to provide informational messages, file storage and transfer and a degree of message exchange to dial-up data terminal or personal computer users.
BURIED CABLE - Cable installed underground in such a way that digging is required to expose it; also known as underground cable.
BURROUGHS DATA LINK CONTROL (BDLC) - Burroughs' proprietary bit-oriented protocol similar to IBM's SDLC.
BURST - 1.) In data communications, an event containing a number of elements, as in a burst of errors; 2.) in other communications areas, a term descriptive of the intermittent occurrence of errors, demands for service or similar events.
BUS - A common physical conductor, to which several units of compatible type are connected in parallel, sharing use of the bus.
BUS INTERFACE UNIT (BIU) - IN LANs, the device furnishing direct connection of a DTE to the LAN bus.
BUSY - The condition in which facilities over which a call is to be transmitted are already in use. Synonym: "off hook." British: "engaged." French: "occupe," reported as "occ" in Telex networks.
BUSY HOUR - The time of day when connections are most in demand in a switched network.
BUSY TONE - A single tone interrupted at 60 impulses per minute in North America, indicating that the called point is already in use. Internationally, variations of both
tone character and interruption rate abound. - Synonym: "station busy signal." British: "number engaged tone."
BYPASS - The connection of two customer locations circumventing use of the Public Switched Network, particularly locally. When transmission facilities of the LEC are rented, but "bypass" the LEC switching machines, a "service bypass" is claimed. If the LEC's physical transmission plant is avoided (as with private microwave), a "facility bypass" is claimed.
BYTE - In computers, a very specifically-sized unit containing 8 bits for the computer to operate on; frequently called a "word" in computer systems.