AT&T 7300 series, 7500 series, 7100 series, 2500 series, 7200 series, 7400 series Bsc, Ccitt, Cpu

GLOSSARY GL-5

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BRI	See basic rate interface.
BSC	See binary synchronous communications.
BX.25	An AT&T version of the CCITT X.25 protocol for data communications.
	BX.25 adds a fourth level to the standard X.25 interface. This uppermost
	level combines levels 4, 5, and 6 of the International Standards
	Organization (ISO) reference model. See also CCITT, Flexible
	Assignment of BX.25 Signaling Ports, packet switching, and X.25.
bypass tie trunk	A one-way, outgoing tie trunk from a tandem switch to a main switch in
	an electronic tandem network (ETN).
byte	A sequence of (usually eight) bits processed together.
Call Transfer into	A feature that enables a covering user to transfer a call to another
AUDIX	extension, typically AUDIX but possibly another covering user, with all
	pertinent call-related information retained. See also AUDIX.
CCITT	(Comite’e Consultatif International Telephonique et Telegraphique) an
	international body that sets universal standards for data communications,
	including Integrated Services Digital Network (ISDN). CCITT members
	are from telecommunications companies and organizations around the
	world. See also BX.25 and Q recommendations.
central office (CO)	The location of telephone switching equipment that provides local
	telephone service and access to toll facilities for long-distance calling.
	More than one CO can serve the same area.
central office (CO) trunk	A telecommunications channel that provides access from a PBX to the
	public network through the local central office.
central processing unit	The part of a computer that interprets and executes instructions. Also
(CPU)	called central processor.
channel	A telecommunications transmission path for voice and/or data.
channel bank	Terminal equipment for a transmission system used to multiplex
	individual channels using frequency-division multiplexing (FDM) or
	time-division multiplexing (TDM).
circuit	1. An arrangement of electrical elements through which electric current
	flows, providing one or more specific functions. 2. A channel or
	transmission path between two or more points.
class of restriction (COR)	On a System 75 or Generic 1, a feature that allows definition of up to 64
	classes of call-origination and call-termination restrictions for telephones,
	telephone groups, data modules, and trunk groups. See also class of
	service.