Module description: 1.The module Operating voltage 5V; 2.Fault-tolerant design, even if the control line is broken, the relay will not operate; 3.The power indicator (green), the relay status indicator (red); 4.Module size: 50mm x 26mm x 18.5mm (L x W x H). Interface: Input VCC: Relay power supply + GND: Relay power supply - IN: Signal trigger input (High or Low Level Signal, select via jumper) Output NO: Relay normally open. COM: Relay Common Pin NC: Relay normally closed. High or Low Level Trigger Select: 1. Use High Level Trigger When ' IN ' input High Level Signal, the ' NO ' connect with ' COM ' When ' IN ' input Low Level Signal, the ' NC ' connect with ' COM ' 2. Use Low Level Trigger When ' IN ' input Low Level Signal, the ' NO ' connect with ' COM ' When ' IN ' input High Level Signal, the ' NC ' connect with ' COM ' 3. High or Low Level Trigger Select Jumper connect with L, Low Level Trigger Jumper connect with H, High Level Trigger Color: As Shown Material: plastic Package Contents: 2 x relay module 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.