... 4.protection circuit 5.video multiplexer Model:SD-S803VCS/R ,3 channel video signal transmit by one coaxial cable video multiplexer with RS485 usded ... in CCTV Maintenance SD-S803VCS/R4CH video/3CH video+1CH negative data1,as ... of video signal can be adjusted at the transmitter according to different camera;7,12V DC power supply,built-in;8, ...