AT&T MERLIN LEGEND Data Manual page 138

Glossary
channel
A telecommunications transmission path for voice and/or data.
channel service unit (CSU)
Equipment used at a customer's premises to provide DS1 facility terminations and signaling compatibility.
checksum
The sum of ones in a sequence of ones and zeros to detect or correct errors in data transmission.
circuit-switched data call
A data call made via a connection exclusively established and maintained between data stations for the duration of the data
call.
clock synchronization
The operation of digital facilities from a common clock.
coaxial cable
A cable consisting of one conductor, usually a small copper tube or wire, within and insulated from another conductor of
large diameter, usually copper tubing or copper braid.
codec (coder-decoder)
A device used to convert analog signals such as speech, music, or television to digital form for transmission over a digital
medium and back to the original analog form.
CO line/trunk jack
A jack that connects an outside line/trunk to the communications system control unit.
common-channel signaling (CCS)
Signaling in which one channel of a group of channels carries signaling information for each of the remaining channels,
permitting each of the remaining channels to be used to nearly full capacity. In the system's DS1 module, channel 24 can be
designated as the signaling channel for channels 1-23 by selecting "common channel" for emulated service when
programming the system. CCS must be used for ISDN-PRI service.
communications system
The software-controlled processor complex that interprets dialing pulses, tones, and/or keyboard characters and makes the
proper interconnections both inside and outside the system. The communications system itself consists of a digital computer,
software, a storage device, and carriers with special hardware to perform the actual connections. A communications system
provides voice and/or data communications services, including access to public and private networks, for telephones and
data terminals on a customer's premises.
commanding
The compression or expansion of the quantizing scale to reduce distortion. See also quantizing.
control unit
The housing, carriers, power supply module, processor module, and line/trunk and station modules of a communications
system.
conversion resource
See modem pool.
cyclic redundancy check (CRC)
An error-detection code used on DS1 facilities with the extended superframe framing (ESF) format.
D
D channel
The 16-kbps or 64-kbps channel carrying signaling or data on an Integrated Services Digital Network Basic Rate Interface
(ISDN-BRI) or 64-kbps channel carrying signaling or data on an ISDN Primary Rate Interface (ISDN-PRI).
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