... is OFF,the same as B/C/D. Extend function:When Jumper is OFF possition, when press button A on the transmitter ... the receiver relay A is ON,the relay B/C/D is OFF;Press remote button 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 OFF;Press remote button D, ...