English: The Goldschmidt tone wheel, a rotary switch invented by German engineer Rudolf Goldschmidt used in early radio receivers for reception of radiotelegraphy (Morse code) signals. This device was used in RCA's transatlantic reception station at Tuckerton, New Jersey as a beat frequency oscillator to receive international telegram traffic. The device consisted of a commutator wheel with many contacts around the rim spun at a high speed by an electric motor, with a sliding spring contact. When connected to a current source the wheel broke the current many times per second, acting as a high frequency generator. The high frequency signal created by the wheel was mixed with the incoming Morse code signal, and created an audible beat frequency that was heard as a tone in the receiver's earphones ,making the pulses of carrier, the "dots" and "dashes" audible. This tone wheel rotated at 4000 RPM and produced a square wave signal of around 40 kHz. Tone wheels were used for a short time around World War 1, until they were replaced by vacuum tube beat frequency oscillators in the 1920s. Later tone wheels were used in electronic organs to generate audio