In a relay, there can be multiple normally open contacts, normally closed contacts, and switching contacts. The normally open contact is in the disconnected position when not powered on, the normally closed contact is in the connected position when not powered on, and the switching contact can switch between the normally open and normally closed states.

Automobile relay is an automatic control device, and when the input quantity (such as electricity, magnetism, sound, light, heat) reaches a certain value, the output quantity will undergo a jumping change. The relays used in cars are typically used to control circuits and implement power paths in switch control circuits, such as lighting and air conditioning systems, heaters, horn signals, and fuel pumps.