The JC-MC-ZN03 door magnetic sensor is mainly composed of two parts: a switch and a magnet. The switch part is made up of a reed switch connected by a lead wire, and is shaped and packaged; the magnet part is encapsulated in a plastic or alloy shell with a corresponding magnetic field strength. After the two are separated or close to a certain distance, it will cause the switch to open, thereby sensing the change of the object's position.