Electromagnetic lock apply to door phone system, fire control passageway, glass door, aluminum alloy door, etc. It can work together with RFID access controller and door phone system in -40 degree to +50 degree working condition. When power is applied the magnetic lock, it turns on the unit's powerful built-in electromagnet. This electromagnet is attracted to the steel armature plate which is mounted on a door, holding the door fast against unauthorized entry. When power to the magnetic lock is turned off, the electromagnet releases the armature plate, allowing the door to open.