AT&T MERLIN LEGEND System Reference Manual page 629

Glossary
automatic-start tie trunk
A tie trunk on which incoming calls are routed to an operator or other designated destination without a start signal. Also
called automatic-ringdown tie trunk or auto-in tie trunk.
auxiliary power unit
A device that provides additional power to the communications system.
B
B channel
For an Integrated Services Digital Network (lSDN), a 64-kbps channel that carries a variety of digital information streams.
such as voice at 64-kbps, data at up to 64 kpbs, wideband voice encoded at 64 kpbs, and voice at less than 64 kbps, alone
or combined with other digital information streams. Also called bearer channel
bandwidth
The difference, expressed in hertz, between the highest and lowest frequencies in a range of frequencies that determine
channel capacity.
barrier code
A password used to limit access to the Remote Access feature of the communication system.
basic carrier
A piece of hardware that holds and connects the processor module; power supply module; and up to five line, trunk or
station modules in the communications system. See also expansion carrier.
Basic Rate Interface (BRI)
A standard Integrated Services Digital Network (lSDN) frame format that specifies the protocol used between the
communications system and a terminal. BRI runs at 192 kbps and provides two 64-kbps voice or B channels and one
16-kbps signaling or D channel per port. The remaining 48 kbps are used for framing and D-channel contention.
baud
In telecommunications applications, a unit of transmission speed equal to the number of signal events per second. See also
bit rate and bits per second.
Behind Switch
A mode of operation in which the communications system control unit is connected to (is "behind') another communi-
cation system.
binary code
An electrical representation of quantities or symbols expressed in the base-2 number system.
bipolar 8 zero substitution (B8ZS)
A line-coding format that encodes a string of 8 zeros in a unique binary sequence using bipolar violation. See also bipolar
signal and bipolar violation.
bipolar signal
A digital signal in which pulses (1 's) alternate between positive and negative. See also alternate mark inversion, alternate
space inversion, bipolar 8 zero substitution, and bipolar violation.
bipolar violation
A condition that occurs when two positive or two negative pulses are received in succession. See also alternate mark
inversion, alternate space inversion, B8 zero substitution, and bipolar signal.
bit (binary digit)
One unit of information in binary notation, having two possible values: zero or one.
GL-2 Glossary