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An electric bell is a mechanical or electronic bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing, clanging or ringing sound.
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.
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole in the center of the coil. The magnetic field disappears when the current is turned off.
He invented a precursor to the electric doorbell (specifically a bell that could be rung at a distance via an electric wire, 1831) [7] and electric relay (1835). [8] His work on the electromagnetic relay was the basis of the practical electrical telegraph , invented separately by Samuel F. B. Morse and Sir Charles Wheatstone .
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.
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.
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.
In later practical receivers the decoherer was a clapper similar to an electric bell, operated by an electromagnet powered by the coherer current itself. When the radio wave turned on the coherer, the DC current from the battery flowed through the electromagnet, pulling the arm over to give the coherer a tap.