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DEFINITY ECS Release 8.2
Administrator’s Guide
555-233-506
Issue 1
April 2000
Glossary and abbreviations
1627
data service unit (DSU)
A device that transmits digital data on transmission facilities.
data terminal
An input/output (I/O) device that has either switched or direct access to a host computer or to a processor
interface.
data terminal equipment (DTE)
Equipment consisting of the endpoints in a connection over a data circuit. In a connection between a data ter-
minal and host, the terminal, the host, and their associated modems or data modules make up the DTE.
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 signal-
ing 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 acknowledgment (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. Com-
monly used to mean the forwarded-to terminal when Call Forwarding All Calls is active.