1 Channel 5V Opto Isolated Relay Module is a simple relay board. 1 channel relay board works from a 5V supply to JVCC for the relays and 0V for the switching signal to relays activate. It uses a transistor to drive the relay & optocoupler used to separate the output. Using these relay board you can easily control high power DC 30V/AC 250V devices or appliances using arduino or microcontroller. It can be connected directly to a microcontroller pin. It has 3 pin terminals output NO COM NC. NO normally open with relay common pin. NC Normally connected with common.