AT&T SYSTEM 25 User Manual page 10

Lights
A steady red light identifies the line you are using or
the line you will be using when you lift the handset.
A steady green light indicates that a line or feature is
in use.
A slow flashing green light indicates an incoming call.
A fast winking green light indicates a call on hold. (A
green light that winks intermittently indicates a call
held temporarily while being transferred or
conference.)
On the Selector Console, a steady red light indicates
either that a voice terminal is off-hook or that a call is
parked on this extension.
On the Selector Console, a flashing red light indicates
a call to you from that voice terminal or an
unanswered call returning to your console.
DDCs and PDCs
When your System 25 was installed, Data Dial Codes (DDCs)
were assigned to data terminals and Personal Dial Codes (PDCs)
were assigned to voice terminals. In most cases, your PDC is
your extension number.
Visitors and those who do not have exclusive use of a voice
terminal may have been assigned Floating Personal Dial Codes
(FPDCs).
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 entry. Also, refer to the
entries for "Directory," "Display," "Inspect," and "Local Display
Functions."
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