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Appendix D. Glossary
D-4 T3SU 300 User Manual 61200217L1-1
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.
control port
The electrical interface between the T3SU 300 and the control terminal. The con-
trol terminal is used to communicate commands to the unit.
CPE
customer premise 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.
CSU
channel service unit. A device used to connect a digital phone line coming in
from the phone company to either a multiplexer, channel bank, or directly to
another device producing a digital signal; for example, a digital PBX, a PC, or
data communications device. A CSU performs certain line-conditioning and
equalization functions, and responds to loopback commands sent from the cen-
tral office. A CSU regenerates digital signals. It monitors them for problems and
provides a way of testing the digital circuit.
CTS
clear to send. A signal on the DTE interface indicating that the DCE is clear to
send data.
data communications equipment
See DCE.
data service unit
See DSU.
dB
decibel. A unit of measure of signal strength; usually the relation between a
transmitted signal and a standard signal source.