A magnetic lock is a magnet that is created when an electrical current is passed through a wire with multiple coils around an iron core, or a solenoid (single coiled wire wrapped around a metal core). When the electrical current is disrupted the metal wire is no longer magnetized. Because of the very nature of an electromagnet, it can not be fail-secure, which means that in the result of an emergency or power outage, the doors will unlock. The built-in feature of unlocking in the result of a power outage (referred to as fail-safe) is the basic operating premise of the electromagnet or maglock.
When there is no emergency or power failure to disable the locks, the magnets can be manipulated with a push-button, keypad, or card reader that temporarily interrupts the electrical current. After a few seconds, the current will return, and once the door has closed it will magnetically bind the door to the door frame. This lock set up is constructed by fixing a plate of magnetic metal (usually iron) to the door, and the electromagnet to the door frame.
Pros The lock will open in the case of an emergency (fail-safe). The lock can be made to open with any electrical signaling method (key code, swipe card, motion sensor, biometrics, etc.) Electromagnets are available with a large selection of holding force options. Commonly, from 600 pounds to 1,200 pounds or more of holding force.
Cons The security can be overcome by interrupting the electricity in the building (referred to as fail-safe). The door may be able to be pried open depending on the gap between the door and frame (force required is based on the magnetic lock holding force).