Relay is a kind of automatil electric switch, when supply with an input value, like electric, magnetic, light or thermal signal,it wall transfer the controlled circuit automatically and make an abrupt change, when the input value decreased to certain degtee,it will resume to former state and make the controlled circuit back to the former stare.

Time relay in the industrial automation system and mechanical equipment component to delay. Generally used for the delay in the industrial automation system and mechanical equipment timing.