1. This design is a relay for industrial application scenarios. It uses Modbus RTU protocol control and 485 signal as the transmission mode. It supports multiple devices controlled by the same host. It can be well applied to industrial automation. With ABS shell and rail buckle, it can be better used in actual environment. 2. The board is equipped with and stable 8bit MCU and SP3485 level conversion chip. 3. Wiring instructions: The relay can be assigned an address in the 485 bus, ranging from 1-255. The corresponding instructions can be sent for the address of the relay, so that the relay receiving the instruction can open and close any controlled circuit. 4. Note: When the relay is energized, the COM terminal and the NO terminal are connected and disconnected from the NC terminal. That is, load 1 works and load 2 does not work. When the relay is not energized or not connected to the power supply, the COM terminal and the NC terminal are connected and disconnected from the NO terminal. That is, load 2 works and load 1 does not work. Power supply voltage: 5-32V (the voltage is better to be 6V for more stability) Communication protocol: Support standard Modbus RTU protocol Communication interface: Support RS485 interface, with 120R terminal resistance dip switch Baud rate: 4800/9600/19200/38400, default 9600bps, support power-off saving Output signal: relay switch signal Due to different batches, there may be differences in product appearance and printed text, which not affect use. Type:RS485 Modbus Relay PRO 4CH Relay Colour:As Shown Material:ABS Package Contents: 1 * RS485 Modbus Relay PRO Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.