Relay

A relay is an electrical control device, which is an electrical appliance that makes a predetermined step change in the controlled quantity in the electrical output circuit when the change of the input quantity (excitation quantity) meets the specified requirements. It has an interactive relationship between the control system (also known as the input loop) and the controlled system (also known as the output loop). Usually used in automated control circuits, it is actually an "automatic switch" that uses a small current to control the operation of a large current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.