Appendix D. Glossary
61200290L1-1 MX2800 User Manual D-3
C-bit
An overhead bit in the DS3 string not used for framing, parity, or alarm indica-
tion.
CCITT
Consultive Committee for International Telephony and Telegraphy. A standards
organization that devises and proposes recommendations for international com-
munications. See also ANSI.
CD
carrier detect. A signal generated by a modem or DSU/CSU indicating the pres-
ence of a carrier signal on a communications link.
channel
A transmission path between two or more termination points; also called a cir-
cuit, facility, line, link, or path.
channel bank
Equipment in a telephone central office or customer premises that performs mul-
tiplexing of lower speed digital channels into a higher speed composite channel.
The channel bank also detects and transmits signaling information for each
channel, thereby transmitting framing information so that time slots allocated to
each channel can be identified by the receiver.
channel service unit
See CSU.
clocking
An oscillator-generated signal that provides a timing reference for a transmis-
sion link. A clock provides signals used in a transmission system to control the
timing of certain functions. The clock has two functions: (1) to generate periodic
signals for synchronization, and (2) to provide a time base.
CPE
customer premises equipment. All telecommunications terminal equipment
located on the customer premises, including telephone sets, private branch
exchanges (PBXs), data terminals, and customer-owned, coin-operated tele-
phones.
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