atcomsystems.ca/forum Forums TDM Business Telephone Systems Nortel Telephones & Systems Door Phone / Door Opening Controller

A third party solution will connect to a trunk port so you must have another line-in available on the phone system.

I have used the Viking which makes different grades of door speakers (vandal resistance). I have also used the Viscount and the TeleDoorBell . The Viscount and TeleDoorBell are cheaper, but not as vandal proof.