1. Onboard and stable 8bit MCU and MAX485 level conversion chip 2. Communication protocol: support standard Modbus RTU protocol 3. Communication interface: support RS485/TTL UART interface 4. Communication baud rate: 4800/9600/19200, default 9600bps, support power-down save 5. Optocoupler input signal range: DC3.3-30V (this input cannot be used for relay control) 6. Output signal: relay switch signal, support manual, flash, flash mode, flash/flash delay base is 0.1S, the flash/flash time can be set to 0xFFFF*0.1S=6553.5S 7. Device address: range 1-255, default 255, support power-down save 8. Baud rate, input signal, relay status, device address can be read by software/ 9. Onboard 4 5V, 10A/250V AC 10A/30V DC relays, which can be activated 100,000 times continuously, with diode overflow protection and short response time 10. On-board relay switch indicator light 11. Power supply voltage: DC7-24V, support DC socket/5.08mm terminal power supply, with input anti-reverse connection protection Type: Relay Module Switch Rated voltage: 4 Channels color:Blue Material:PCB Package Contents: 1 x Relay Module Only the above package content, other products are not included. Note: Light 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.