AT&T Door Phone Controller Installation And Operation Manual page 65

Answering a Call Sent
From the Door Phone
Opening door will terminate
station mode access.
Calling the Door
Speaker
number, 1 or 2 (these can be selected by pressing ##1 or ##2
once connection to the speaker has been made). Any
additional presses on the door speaker push button will be
ignored while the Door Phone Controller is off-hook.
When a person answers the ringing telephone, the Door Phone
Controller will establish two-way communications with the door
speaker.
To open the door, the person inside the building either enters
the Door Code on the telephone's keypad or presses the
customer provided door-unlock push button.
Either of these actions will close the metallic contacts which
activate the customer provided electric door release.
To initiate a call to the Door Speaker, the person inside the
building simply takes the telephone off-hook and dials the
station phone number of the door speaker.
Installation - Dedicated Station Port 5-9