Fireboy - RCM5 Relay Control Module

The old CMD-4M-RLY requires two parts to replace it the CMD5-MDI Interconnect CO Alarm and the RCM5 Relay Control Module. If your CO Alarms are interconnected and you do NOT have generator shutdown, you can use just the CMD5-MDI units and interconnect them. If your boat is equipped with generator shutdown you need the RCM5.