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An electromagnetic door holder (electromagnetic door holder and release or hold-open device, sometimes informally called a mag hold open or electric doorstop) is a simple electromechanical mechanism which can be used to hold a fire door or security door open until given a signal to release.
A fail-secure locking device remains locked when power is lost. Fail-safe locking devices are unlocked when de-energized. Direct pull electromagnetic locks are inherently fail-safe. Typically the electromagnet portion of the lock is attached to the door frame and a mating armature plate is attached to the door.
Heron used a similar application to open the gates to the city. [2] In 1931, engineers Horace H. Raymond and Sheldon S. Roby of the tool and hardware manufacturer Stanley Works designed the first model of an optical device triggering the opening of an automatic door. The invention was patented and installed in Wilcox's Pier Restaurant in West ...
Some are built on top of a standard door closer. To open the door, the operator forces the closer in the opening direction. Then, the closer closes the door. The user may open the door manually, using just the door closer. In case of power failure while the door is open, the closer itself closes the door. Some are built without a door closer.
There are specialty electric strikes that hold the electric strike keeper open until the door with the extended deadbolt closes back into the electric strike to "recapture" the extended deadbolt. Mortise type locksets tend towards larger projecting latches from the door to engage deeper in the frame and electric strikes used for these locking ...
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