Looks like a BITRON AN 0002 but your photo of the wiring terminals is not completely clear.
C7 Call (electronic)
11 Call (AC Buzzer)
1 Speech In (Speaker)
2 Speech Out (Mic)
9 Lock
6 Common
If your system uses AC buzzer across 11 and 6 you can disconnect the wire from 11 and wire a doorchime...