AT&T System 25 - Manual (Page 10)

Data Dial Code (DDC)
When your System 25 was installed, Data Dial Codes (DDCs)
were assigned to data terminals. If
you have a data terminal
associated with your System 25, you will receive separate
information regarding its use.
Personal Dial Code (PDC)
Personal Dial Codes (PDCs) were assigned to telephones. In
most cases, your PDC is your extension number. If a telephone
is shared by two or more people, each person may have been
assigned their own “floating” extension number (FPDC).
Floating extension numbers (FPDCs) are also used as a
convenience for visitors, and for people who are not
permanently assigned to a specific location.
Display Unit
The console’s built-in display provides visual information about
incoming and outgoing calls. Use the procedures and sample
screens shown at the end of each feature entry. Also, refer to
the entries for “Directory”, “Display”, “Inspect”, and “Display
Functions”.
Queue Status
System 25 “stacks” calls to a busy console in a waiting line (a
queue). These queued calls are then sent to the console, one at
a time, as the attendant becomes available. The number of calls
waiting in the queue is shown on the right side of the Screen 1
display. If one to nine calls are waiting for to be answered, the
actual number appears. A queue of ten or more calls is indicated
by "!".
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