5V 1 Channel SSR G3MB-202P Solid State Relay Module 240V 2A O/P is based on the Omron G3MB SSR relay which can control up to 2A at 240VAC. This is a 1 Channel SSR relay module which has 3 separate terminals, NO (Normal Open), COM (Common), NC (Normal Closed). A Solid State Relay is similar to a mechanic relay But it is a low-level trigger relay, So the relay will turn on at LOW level input (that is Digital 0 will turn ON the relay). And hence it can be controlled through a digital signal. Solid State Relay generates no noise and has a much longer lifespan in compared to the traditional mechanic relay.