ZAP GARAGE DOOR OPENER 871 External Radio and Accessory Interface Module. This interface is used to connect three-channel receivers, microwave sensors, or even loop detectors to the Operator. Input terminals on the board include Open, Close, Stop, Common, and Cycle. To install this interface 14-20 AWG wiring is required. The module comes standard with a 6 position dual direction plug for easy installation to the main board.