4-channel relay control board module with an optocoupler, 4-way relay module for Arduino 4-channel relay output modules, relay output contacts 250A 10A. Input IN1, IN2, IN3, IN4, the signal line LOW effective. VCC, GND power input, can relay a separate power supply relay power input of JD-VCC. Uses: support all MCU control. The industrial sector PLC control smart home control. Wiring: VCC: positive power supply system GND: System power supply negative IN1 - IN4: relay control ports