English: 100 kW Goldschmidt alternator at Eilvese, Germany. The Goldschmidt alternator, invented in 1908 by Rudolph Goldschmidt, was a rotating machine that generated high frequency alternating current, used as a radio transmitter from 1910 until about 1930. The Goldschmidt machine generates high frequencies without requiring excessive rotor speeds by using the rotor as a frequency multiplier as well as an AC generator. Tuned circuits called "reflector" circuits, attached to the stator and rotor (the capacitor banks against the walls) cause the machine to produce power at a harmonic (multiple) of the alternator frequency. In this machine, the 250 HP 220 VDC drive motor (left) turns the 3 ft diameter, 5 ton rotor (right) at 4000 RPM. The rotor has 360 narrow magnetic poles in its periphery, and therefore the fundamental frequency produced by the rotor is 24 kHz. The complicated reflector circuits cause the rotor to generate an alternating current at 4 times the fundamental frequency, 96 kHz, which is applied to the antenna through a transformer. The station transmitted text messages in Morse code, by the operator switching the DC power to the rotor on and off with a telegraph key. The machine was used for transatlantic wireless telegraphy traffic, exchanging messages with a similar machine in Tuckerton, New Jersey, USA.