If it helps any, my 74551 has a magnetic sensor and two other wires currently with one connected to COM and the other to connected to N/O. The garage door opener is a Craftsman 41A-5021. It is pretty old, like 15 years or more. I have tried all kinds of combinations for the Garage door sensor in the ISY994I (latching, momentary:a,momentary:B and mometary:C but no matter what I try, only ON commands seem to do anything and toggle the garage door between OPEN and CLOSE. OFF does nothing.