Do they specify what types of smoke detectors/alarms are to be used? Alarm companies frequently monitor the AC/DC smoke alarms we install by using a relay designed for the smoke alarms. The relay doesn’t count as one the 12 max alarms. Even if you are required to replace all of the smoke alarms the current wiring between them can still be used. If you disconnect the power source and can get a wire from the alarm panel to any of the alarms you should be ok. Most alarm panels will work with 2-wire or 4-wire smoke detectors.
Curt
