In the video surveillance system, the signals transmitted by the transmission system are divided into two groups, one is a video signal, the video signal is transmitted through a coaxial cable, a twisted pair cable, an optical fiber, etc., one group is a control signal, and is transmitted by using a 485 signal mode. Generally, shielded twisted pair is used for transmission. Generally, the video signal line is directly connected to the surveillance camera, and the control signal line is connected to the decoder that controls the operation of the surveillance camera.
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When the construction party lays the line, the video signal line and the control signal line are bundled together, so that the line is more cost-effective, such as the cost of the casing and the perforation of the line. Since the monitoring system requires that all video signals and control signals be centralized to the monitoring management center for unified management, and the video signal lines are transmitted by video coaxial cable, supporting the star topology, most of the lines are arranged in a star topology, but Since the control signal line is a 485 bus, it is required to be connected in a daisy-chain manner by hands. The layout of the star-shaped connection causes signal reflection to cause instability of the system, and must be arranged in a bus topology, thus causing a video signal line and a control signal line. Two different topologies must be taken, which inevitably increases the cost. The control code distributor can be used to solve the problem by arranging the 485 bus into a star topology.
For an intelligent building construction project, video surveillance cameras are installed on each floor to continuously monitor the entire public area of ​​the building. The monitoring and management center is set up in the monitoring room on the first floor. The constructor pulls a line from each floor directly to the monitoring. The room is arranged in a star topology, and the video signal line and the control signal line share a pipe slot. After the line is laid, debugging is performed to find that the system is unstable, and there is always a case of control failure, which is passed with Shenzhen Dingxin Hongda Technology. Co., Ltd. communicated and found that the control signal line can only support bus connection due to 485 signal transmission. The star connection will cause signal reflection and communication failure. Re-laying the line, the construction period can not catch up and the cost is huge. The control code distributor can effectively solve the problem. The control code distributor can divide one 485 bus into multiple 485 buses, each drive is independent, isolated from each other, no signal exists. The reflection problem makes the 485 bus star topology stable communication.
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