I have a Nortel bst doorphone that a client wants to keep using after switching out the phone system for a UCM 6510. Is it possible to use these doorphones on this system? With an onboard FXS port or port on an ht-802 ATA?
Usually yes if that doorphone use standard PSTN communication.
But connection will depend how this doorphone work (how it establish call).
NO, the Nortel BST is digital, not analog.
If it SIP complaint then it will work.
Not SIP either. Digital to Nortel, thought to be made by Algo.
The BST doorphone is proprietary and as far as I recall only works with Avaya CM and can only unlock remotely using Avaya handsets.