Features: Board around with four fixed screw holes, hole diameter 3.1mm, easy to install and fixed Relay selection of high-quality loose relay, single-pole double-throw. A common end, a normally open end, a normally closed end Optocoupler isolation, good anti-interference Low level pull-in, high-level release. Pull the status indicator light, release the status indicator is off VCC for the system power, JD_VCC for the relay power. Plug in the jumper cap Specifications- Relay Type Low-Level Trigger Logic Input (V) 3.3 ~ 5 Trigger Voltage (VDC) 5 Switching Voltage (VAC) 250@10A Switching Voltage (VDC) 30@10A