I am trying to record a IV Callmaster using multiple registration and I am getting:
"Error   0   DEVICE [26589] did not register: Registration Reject reason: undefinedReason
Shared control denied because of incompatible set type - only DCP and IP phone w/speaker are allowed."

I found in the AES Programmer's guide I found that the Physical Device Services does not support devices without a speaker phone.
"Devices that are not equipped with a speaker-phone (e.g. CallMaster) are not supported."

Is this the reason that I am not able to register the Callmaster phones?

That is correct.

Martin