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Electric bells are typically designed to operate on low voltages of from 5 to 24 V AC or DC. Before widespread distribution of electric power, bells were necessarily powered by batteries, either wet-cell or dry-cell type. [2] Bells used in early telephone systems derived current by a magneto generator cranked by the subscriber.
The Oxford Electric Bell or Clarendon Dry Pile is an experimental electric bell, in particular a type of bell that uses the electrostatic clock principle that was set up in 1840 and which has run nearly continuously ever since. It was one of the first pieces purchased for a collection of apparatus by clergyman and physicist Robert Walker.
As the bell swings higher the sound is projected outwards rather than downwards. Larger bells may be swung using electric motors. In some places, such as the Salzburg Cathedral, the clapper is held against the sound bow with an electric clasp as the bell swings up. The clasp would release the clapper to provide a cleaner start to ringing.
The system of operation of the Franklin clock considers that the electrostatic force generated by an electric field is used to move the pendulums that strike two metal bells. [9] [10] The Franklin bells uses a metal rod as a lightning rod to attract current. One bell is connected to the lightning rod and the other bell is connected to the ground.
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]
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.
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Early devices were based on an electromechanical system identical to an electric bell without the metal gong. Similarly, a relay may be connected to interrupt its own actuating current, causing the contacts to buzz (the contacts buzz at line frequency if powered by alternating current) Often these units were anchored to a wall or ceiling to use it as a sounding board.