AT&T MERLIN LEGEND Installation & Maintenance Manual page 692

Glossary
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.
companding
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).
D4 framing format
A framing format consisting of
a sequence of individual
frames of 24 eight-bit slots,
and 1 signal bit (193 bits) in a
12-frame superframe. See
also extended super frame
format.
Glossary GL-7