... .video multiplexer Model:SD-S803VCS/R ,3 channel video signal transmit by one coaxial cable video multiplexer with RS485 usded ... video +1channel negative RS485 control signal optionally through selector switch;3,RS 485 control interface can be driven by special chip ... better video effect;6, brightness degree of video signal can be adjusted at the transmitter according to different camera;7,12V DC power ...