Relay is an electromagnetic switch that principle works using the principle of electrical coils. A coil air-intikan a soft iron plates that when electric current flowing through the soft iron plates will be a magnet. The magnets attract or repel a spring contact interface and consequently there will be contact and loose contact of the interface. These principles can be used as the basis for an automatic switch. Relay serves as a liaison and as a circuit breaker or automatic switch.

All relays have the basic parts which include contact Stationari (silent contacts), contacts that can move (movable contack), armature, and magnets.
Each relay has a normally open and normally closed or a combination of both. A relay can have more than one arrangement of contacts that can be combined as normally closed or normally open.
The movement of the armature when energized, can cause contact arrangement normally open or closed position moves to the opposite of the normally closed position to the open.