a power outage, disabling security. Expensive in comparison to mechanical locks. Requires additional hardware for safe operation. Installation The magnetic lock is suitable for both in-swinging and out-swinging doors. Brackets (L bracket, LZ bracket, U bracket) are used to orient the armature for use with both applications. Filler plates are also used to provide a large, flat mounting area on the door frame when the electromagnet is larger than the available mounting space on the door frame due to the frame's geometry. The magnetic lock should always be installed on the secure side of the door. Most installations are surface mounted. For safety, magnetic lock, cables, and wires should be routed through the door frame or flush mount with wire moulding. Installation is straightforward. With in-swinging applications, the electromagnet is typically installed in the opening corner of the door at the door's header. Maglocks can also be installed vertically in the door opening when they are furnished with a full length housing. With this configuration the armature is through-bolted through the door and oriented to mate with the face of the electromagnet. The armature plate and electromagnet must touch in order to provide locking holding force. With out-swinging applications, the electromagnet is typically installed on the side of the door header. In this configuration, the armature is mounted on a Z shaped bracket that orients the armature to mate with the electromagnet. Magnetic locks are almost always part of a complete electronic security system. Such a system may simply consist of an attached keycard reader or may be more complex, involving connection to a central computer that monitors the building's security. Whatever the choice of locking system, fire safety is an important consideration. Other variations and improvements on the electromagnetic locks have been developed. The most remarkable is the shear lock, where the armature does not directly pull off the face, but the load is instead in shear, like a mechanical stop. The shear magnetic lock allows a door to swing in both directions, as opposed to the original (and now ubiquitous) direct pull type, which normally works either in an in-swing or out-swing configuration. In order to provide the shear magnetic lock with the appropriate holding force, then two pins lock the armature onto the magnet itself, and ensure that the magnet locks into place. An improved 'shear' electromagnetic lock was patented on May 2, 1989, by Arthur, Richard