Tonewheel

A tonewheel or tone wheel is a simple electromechanical apparatus used for generating electric musical notes in electromechanical organ instruments such as the Hammond organ and in telephony to generate audible signals such as ringing tone.

[1] It was reinvented around 1910 by Rudolph Goldschmidt for use in pre–vacuum-tube radio receivers as a beat frequency oscillator (BFO) to make continuous wave radiotelegraphy (Morse code) signals audible.

The tonewheel assembly consists of a synchronous AC motor and an associated gearbox that drives a series of rotating disks.

As the bump moves past, this concentrating effect is reduced again, the magnetic field weakens slightly, and an opposite current is induced in the coil.

The tonewheel was independently invented in 1910 by Rudolph Goldschmidt as a beat frequency oscillator in early radio receivers to make continuous wave radiotelegraphy (Morse code) signals audible, before the existence of the vacuum tube.