board four weeks with four screws holes, hole diameter 3.1mm, easy to install and fixed
relay of high quality loose music relays SPDT. A common terminal, a normally open, one normally closed terminal
optocoupler isolation, good anti-jamming
low pull, high release. Energisation status indicator light, release status LED is off
VCC of system power, JD_VCC relay power. You can plug in jumpers