Electric bell
From Wikipedia, the free encyclopedia
An electric bell is a mechanical bell that functions by means of an electromagnet. When the switch is pushed 'on', current flows through the coil. The coil becomes an electromagnet, attracting the metal strip. This moves the clanger to hit the bell, but also breaks the circuit. The coil is no longer a magnet, so the clanger moves back. The circuit is thus restored. The bell keeps ringing until the switch is released.
Two early applications of the electric bell were the telephone and doorbell. Early telephones used electric bells to indicate that there was an incoming call. Doorbells were used by visitors to indicate their presence at the external door of a dwelling or business. Though still in use, the electric bell mechanisms in both telephones and doorbells now compete with non-mechanical noisemaking technologies including digitally recorded sounds played back through a speaker.