The module uses authentic quality relay, normally open interfaces, Maximum load: AC 250V / 10A, DC 30V / 10A; Use SMD isolation optocoupler, ability to drive, stable performance.Trip 5mA current. The operating voltage of the module 5V; The module can be high or low by a trigger of the jumper setting. The fault-tolerant design, even if the command line is case sensitive, the relay won't work; The power indicator (green), the flag of the State of the relay (red) Interface module: 1. DC: positive supply (VCC) 2. DC: power negative (GND) 3. IN: control relay may be high or low level Relay outputs: 1. NO: normally open relay interface 2. COM: Common interface relays 3. NC: normally closed relay interface High and low level triggering options: It is low level trigger when the jumper connects to bottom pin It is high level trigger when the jumper connects a high pin Package contents: 1 x 1-channel H/L level Relay module optocoupler shutter button Four hole mounting bolts, 3.1mm diameter size:50mm x 26mm x 18.5mm (L x W x H) Material:PCB colour:Blue Package Contents: 1 x Relay Module Only the above package content, other products are not included. Note: Light shooting 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.