The ZAP garage door opener 871 Interface Expansion Module available at North Shore Commercial Door is a plug-in module with the option for additional expansion room for inputting external control devices. So if you have a three-channel external radio control receiver for open stop and close function via radio transmitter, microwave sensors and loop detectors, you can input those in the 871 Interface Expansion Module. Open, Stop, Close, Common and Cycle input terminals are all provided. A 24VDC output terminal is provided. If the power supply is overloaded, an LED illuminates so you know there is a fault or that a device is drawing excessive current. The 871 requires 14-20 AWG wiring and plug-in mounting. It comes with a six-position dual direction plug that slides in.