ITEM NAME:Modbus RTU 4 Way Relay Module 4 Switch Volume Road Input 485 Communication A#S Product Description Description: Description: Relay communication: 485 communication in multi-unit network. Based on MBDBUS-RTU protocol, the default address is 1. Users can modify the address by themselves through instructions. Note: IN1 - IN4 is used to read switch status through 485, not through input control relay output. IN1-IN4 switch state needs to read the switch state every time the computer inquires, and can not send data to 485 actively. Note: IN1-IN4 does not connect 220V. Specification: Size: 76mm*67mm*17.5mm/2.99*2.63*0.68'' Weight: 79g Connection Mode: 1. IN1 - GND (default is high level, low level after switching on) computer sends instructions to read switch status. 2. IN2 - GND (default is high level, low level after switching on) computer sends instructions to read switch status. 3. IN3 - GND (default is high level, low level after switching on) computer sends instructions to read switch status. 4. IN4 - GND (default is high level, low level after switching on) computer sends instructions to read switch status. Note: Please allow 1-3mm differs due to manual measurement. Due to the different display and different light, the picture may not show the actual color of the item. Thanks for your understanding. Included: 1 X Modbus RTU 4 Way Relay Module.Included: 1 X Modbus RTU 4 Way Relay Module. Relay communication: 485 communication in multi-unit network. IN1 - GND (default is high level, low level after switching on) computer sends instructions to read switch status.