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Glossary and Abbreviations
555-230-024GL-16 Issue 5 January 1998
dB
Decibel
dBA
Decibels in reference to amperes.
dBrnC
Decibels above reference noise with C filter.
DC
Direct current
DCE
Data-communications equipment
D-channel backup
Type of backup used with Non-Facility Associated Signaling (NFAS). A primary D-channel
provides signaling for an NFAS D-channel group (two or more PRI facilities). A second D-channel,
on a separate PRI facility of the NFAS D-channel group, is designated as backup for the
D-channel. Failure of the primary D-channel causes automatic transfer of call-control signaling to
the backup D-channel. The backup becomes the primary D-channel. When the failed channel
returns to service, it becomes the backup D-channel.
DCO
Digital central office
DCP
Digital Communications Protocol
DCS
Distributed Communications System
DDC
Direct Department Calling
DDD
Direct Distance Dialing
delay-dial trunk
A trunk that allows dialing directly into a communications system (digits are received as they are
dialed).
denying a request
Sending a negative acknowledgement (NAK), done by sending an FIE with a
return error
component (and a cause value). It should not be confused with the denial event report that
applies to calls.
designated voice terminal
The specific voice terminal to which calls, originally directed to a certain extension, are
redirected. Commonly used to mean the forwarded-to terminal when Call Forwarding All Calls is
active.
dial-repeating trunks
A PBX tie trunk that is capable of handling PBX station-signaling information without attendant
assistance.
dial-repeating tie trunk
A tie trunk that transmits called-party addressing information between two communications
systems.