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GLOSSARY GL-9
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DDC See Direct Department Calling.
DDD See direct distance dialing.
dedicated line Also known as a private or leased line. It is for the exclusive use of the
leasing party.
dedicated switched
connection (DSC)
A feature that functions as a hardwired link between two ports on a
System 85 (R2V4) or Generic 2 communications system, providing a full-
time line between the assigned endpoints. Once administered, the
connection remains intact until removed. Also called nailed-up
connection. See also permanent switched connection.
default dialing A terminal dialing feature that automatically originates a call to a
preassigned number if the user enters a carriage return without first
entering an address in response to a dial prompt.
demultiplexer A device used to separate two or more signals that were previously
combined by a compatible multiplexer and transmitted over a single
channel.
dial access code (DAC) A dial code assigned to a feature for activation of the feature from the
communications-system station set. See also feature-access code and
trunk-access code.
dialed number
identification service
(DNIS)
A display provided to the answering agent of a service or project, or of the
number called by the caller, so that agents grouped in one split can answer
calls appropriately for different services. DNIS can also be sent to a host
computer or other adjunct.
digital The representation of information in discrete elements such as off and on
or 0 and 1.
digital communications
protocol (DCP)
An AT&T proprietary protocol used to transmit both digitized voice and
digitized data over the same communications link. A DCP link is made up
of two information (I-) channels and one signaling (S-) channel.
digital data Data represented in discrete, discontinuous form, usually binary. This is
in contrast to continuous analog data, usually represented in sine wave
form.
digital facility A switching or transmission facility specifically designed to handle digital
signals.