Module parameters: 1 Size: 75mm (length) x 55mm (W) x 19.3mm (height); 2. Weight: 58g; 3. PCB Color: Blue; 4 board four weeks with four screw holes hole diameter 3.1mm easy to install and fixed; 5 Relay selection of quality loose music relays SPDT. A common terminal a normally open one normally closed terminal; 6 optocoupler isolation good anti-jamming; 7 low pull high release. Energisation status indicator light release status LED is off; 8. VCC for the system power JD_VCC for the relay power. Default hair 5V relay plug the jumper cap to; 9 Relay Maximum output: DC 30V/10A AC 250V/10A Wiring: VCC: positive power supply system GND: System power supply negative IN1 - IN4: relay control ports