The remote control decoder needs to be installed on site; the communication transmission cable between the video decoder and the video matrix switching host of the control center usually adopts 2-core shielded communication cable (RVVP) or 3 types of twisted pair UTP, and each core Sectional area of 0.3mm2 ~ 0.5mm2; select the basic principles of communication cables is the longer the distance, the greater the diameter; RS-485 communication provides basic communication distance is 1200m, but in the actual project selected RVV2-1.5 sheath line The communication length can be extended to more than 2000m.