The vehicle detector in the tunnel is responsible for counting section traffic and occupancy, and the information board is responsible for issuing speed limits and prompt texts. The control side of both is mostly an RS485 bus. A reliable way to move this type of low-speed signal to the management office along with the image is to use a video optical transceiver with a reverse data channel.

First distinguish which line goes to which bus

The vehicle detector is usually hung on a counter or detector, and the output is collected; the information board is the command terminal sent down from the management office. Don't try to save trouble and connect them to the same group of 485 ports.8-channel video + 1-channel reverse 485 data video optical transceiverOnly one reverse 485 is left, which is suitable for grouping similar devices into one bus; when vehicle inspection and intelligence belong to two buses, additional2-way bidirectional RS485 data optical terminalIt is carried alone, and the direction and port are correct.

The baud rate must be consistent at both ends of the protocol

• The baud rate of the data port of the optical transceiver must be consistent with that of the vehicle detector and the information board controller. The common baud rate is 9600 or 19200. If the two ends are not synchronized, the data will not be received or the data will be garbled.
• The transparent transmission model only changes the level without changing the protocol. The private instructions of the information board are issued as usual, and there is no need to change the controller program.
• 485 is differential half-duplex. If there are too many stations on the same bus, it must be divided into segments. When the distance from the tunnel entrance to the tunnel is long, equipment must be added according to segments.

Wiring and identification determine whether it can be maintained or not.

The A/B lines have the same color code throughout the tunnel. If they are connected incorrectly, there will be no reception in a large area. It is recommended that each information board and each vehicle detector register the bus number and port number. The management office can determine which section the fault lies in by comparing it with a table. Wolflight also uses this idea to provide wiring and point table templates in tunnel project delivery. The construction team and operation and maintenance team look at the same table, reducing the number of people sent back and forth. Separate the bus, align the baud rate, and unify the logo, and the reverse 485 polishing will be stable.