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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.
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]
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]
4 - non-magnetic member 5 - conducting member 6 - magnetic member 7 - insulating piece. The most common type of reed switch contains a pair of magnetizable, flexible, metal reeds whose end portions are separated by a small gap when the switch is open. The reeds are hermetically sealed within a tubular glass envelope.
A non-contact method based on magnetic induction was preferred, to eliminate the problems caused by snowfall and day-to-day wear of the contacts which had been discovered in existing systems. The Strowger-Hudd system of Alfred Ernest Hudd ( c. 1883 – 1958) used a pair of magnets, one a permanent magnet and one an electro-magnet, acting in ...
Alarm.com, Inc. is an American technology company that provides cloud-based services for remote control, home automation, and alarm monitoring services. Monitoring services may involve contracts through third-party contractors such as ADT .