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2. Security alarm - Wikipedia

   en.wikipedia.org/wiki/Security_alarm

   A security alarm is a system designed to detect intrusions, such as unauthorized entry, into a building or other areas, such as a home or school. Security alarms protect against burglary ( theft ) or property damage , as well as against intruders.

3. Reed switch - Wikipedia

   en.wikipedia.org/wiki/Reed_switch

   The contacts are usually normally open, closing when a magnetic field is present, or they may be normally closed and open when a magnetic field is applied. The switch may be actuated by an electromagnetic coil , making a reed relay , [ 2 ] or by bringing a permanent magnet near it.

4. Tattle-Tape - Wikipedia

   en.wikipedia.org/wiki/Tattle-Tape

   The tape consists of a magnetic metal strip embedded in a strip of thick, clear adhesive tape. This tape is usually affixed deep between the pages of a paperback book, or between the spine and binding for a hardcover book. When the magnetic strip in the tape is sensitized, an alarm will sound when the item passes through a special gate ...

5. Electromagnetic door holder - Wikipedia

   en.wikipedia.org/wiki/Electromagnetic_door_holder

   An electric current typically energizes the electromagnet to attract and hold the steel plate, keeping the door open. Unlike electromagnetic locks, the magnetic attraction of an electromagnetic door holder is usually weak enough that it can be manually overpowered at any time by anyone, allowing the door to close. [citation needed]

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   Discover the latest breaking news in the U.S. and around the world — politics, weather, entertainment, lifestyle, finance, sports and much more.

7. Edwin Holmes (inventor) - Wikipedia

   en.wikipedia.org/wiki/Edwin_Holmes_(inventor)

   In this way, he quickly assembled a 700-alarm network, which his father then copied in New York. [8] In 1878, Holmes became the president of the newly established Bell Phone Company. While he sold his interests two years later for US$100,000, [9] he kept his rights to use the company phone lines for his alarm system. [8]