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A simple electromagnetic door holder consists of a strong electromagnet, usually attached to a wall or mounted in a floor pedestal enclosure, next to the door it controls. The mechanism may be mounted near the floor, at the upper corner of the open door, or at any convenient height along the latch edge (away from the hinged edge).
Video door phone indoor terminal.. Going a little further in time, we find video door phones featuring a video installation apart from the classical audio. In these cases, the intercom plate has the same structure as the previous version but features a video monitor connected to a surveillance camera that allows inspecting the person who pressed the button and part of the surrounding area.
The most widely used form is the interrupter bell, which is a mechanical bell that produces a continuous sound when current is applied. See animation, above. The bell or gong (B), which is often in the shape of a cup or half-sphere, is struck by a spring-loaded arm (A) with a metal ball on the end called a clapper, actuated by an electromagnet ...
Doorbell mechanism from 1884 in Andrássy Avenue, Budapest Antique mechanically operated shop doorbell on a torsion spring. William Murdoch, a Scottish inventor, installed a number of his own innovations in his house, built in Birmingham in 1817; one of these was a loud doorbell, that worked using a piped system of compressed air. [1]
Since electromagnetic locks do not interact with levers or door knobs on a door, typically a separate release button that cuts the lock power supply is mounted near the door. This button usually has a timer that, once the button is pressed, keeps the lock unlocked for either 15 or 30 seconds in accordance with NFPA fire codes.
Electronic keypad lock. A smart lock is an electromechanical lock that is designed to perform locking and unlocking operations on a door when it receives a prompt via an electronic keypad, biometric sensor, access card, Bluetooth, or Wi-FI from a registered mobile device. These locks are called smart locks because they use advanced technology ...
Shapiro, David E. (2001). Your Old Wiring. New York: McGraw-Hill. ISBN 978-0071357012. Written for home owners and do-it-yourselfers. Shapiro, David E. (2010). Old Electrical Wiring: Evaluating, Repairing, and Upgrading Dated Systems (2nd ed.). New York: McGraw-Hill. ISBN 978-0071663571. Written for professional electricians and advanced ...
The most basic type of electronic lock is a magnetic lock (informally called a "mag lock"). A large electro-magnet is mounted on the door frame and a corresponding armature is mounted on the door. When the magnet is powered and the door is closed, the armature is held fast to the magnet. Mag locks are simple to install and are very attack ...
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