<P> Electric bells are typically designed to operate on low voltages of from 10 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 . Bells used in early telephone systems derived current by a magneto generator cranked by the subscriber . In residential applications, a small bell - ringing transformer is usually used to power the doorbell circuit . So that bell circuits can be made with low - cost wiring methods, bell signal circuits are limited in voltage and power rating . Bells for industrial purposes may operate on other, higher, AC or DC voltages to match plant voltages or available standby battery systems . </P> <P> The interrupter bell evolved from various oscillating electromechanical mechanisms which were devised following the invention of the electromagnet by William Sturgeon in 1823 . One of the first was the oscillating electric wire invented by James Marsh in 1824 . This consisted of a wire pendulum dipping into a mercury trough, suspended between the poles of an electromagnet . When current was passed through the wire, the force of the magnet made the wire swing sideways, out of the mercury, which broke the current to the magnet, so the wire fell back . The modern electric bell mechanism had its origin in vibrating "contact breaker" or interrupter mechanisms devised to break the primary current in induction coils . Vibrating "hammer" interrupters were invented by Johann Philipp Wagner (1839) and Christian Ernst Neeff (1847), and was developed into a buzzer by Froment (1847). John Mirand around 1850 added a clapper and gong to make the standard electric bell for use as a telegraph sounder . Other types were invented around that time by Siemens and Halske and by Lippens . The polarized (permanent magnet) bell used in telephones, which appeared about 1860, had its beginning in the polarized relay and telegraph developed by Werner Siemens around 1850 . </P>

Draw the diagram of an electric bell and explain its working