Magnetic Preservation Relay is a new type of relay which has been developed in recent years, and it is also an automatic switching device. As with other electromagnetic relays, it plays a part of connecting and disconnecting in circuit. The difference is that the normally open and normally closed state of magnetic maintenance relays are entirely dependent on the permanent magnet steel, the conversion of switch state is triggered to complete by a certain width of pulse signal. When the contact of the relay needs to open or close, only need the positive (reverse) DC pulse voltage to motivate the coil, and the relay completes the transition of opening and closing state in an instant. Usually when the contact is in the holding state, the coil does not need to continue to power, the magnetic force of permanent magnet can maintain the status of the relay.