Maglock

A maglock (officially known as an electromagnetic lock) is a locking device that consists of an electromagnet and an armature plate. There are two kinds of electromagnetic lock. Locking devices can be either "fail safe" or fail secure". A fail-secure locking devices remains locked when power is lost. Fail-safe are unlocked when de-energized.

Maglocks come in all shapes and sizes, and are found on reinforced doors and firearm rails alike.