... C/D.Extend function:(When jumper is off position) press A on the transmitter, receiver A goes on 2 seconds, then goes off ... B/C/D.3) Interlock modelPress remote button A, the receiver relay A is on, the relay B/C/D is ... B, the receiver relay B is on, the relay A/C/D is off.Press remote button C, the receiver ... relay C is on, the relay A/B/D is offPress remote button D, the receiver relay ...