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Exterior alarm bell box. If a potential intruder tries to enter into a house, they test whether it is closed and locked, uses tools on openings, or/and applies pressure, creating low-frequency sound vibrations. Before the intruder breaks in, the infrasound detector automatically detects the intruder's actions.
The housing of the bell box may be manufactured from wood, metal, or plastic. The basic core component of a conventional bell box is an electromagnet and a bell or other metal piece, some of which create a repetitive sound. [1] The bell sound is normally created inside the box, although the unit may have bells mounted on the outside of the box.
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]
The word alarm comes from the Old French a l'arme meaning "to the arms", or "to the weapons", telling armed men to pick up their weapons and get ready for action because an enemy may have suddenly appeared. [1] The word alarum is an archaic form of alarm. It was sometimes used as a call to arms in the stage directions of Elizabethan dramas. [2]
Dual-loop is a method of electrical circuit termination used in electronic security applications, particularly modern intruder alarms. It is called 'dual-loop' because two circuits (alarm and anti-tamper) are combined into one using resistors. Its use became widespread in the early 21st century, replacing the basic closed-circuit system, mainly ...
ADT began to expand into new areas, such as fire alarms and security alarms, between 1910 and 1930, but was kept separate from AT&T's Holmes alarm business. ADT became a publicly traded company in the 1960s. [12] In 1964, ADT was found to be a monopoly in restraint of trade. It was shown to provide almost 80% of the central station alarm ...