In automation industries,relay is a common device used for control application.Basic operation of  electrical relay is a device that changes the state of a circuit in response to it being energized or de-energized by that or another circuit.

It function to open or close the circuit or contact and respond depend on signal that we gave it to the magnetic coil.It have normally open and normally close contact that we can choose when design the control circuit for our application.

For generally understanding,relay also may consider as a amplifier and controller.It only a small device in automation circuit but it have important roles to make our system running accordingly. read more