Alexanderson alternator
In 1904 radio pioneer Reginald Fessenden placed an order for a high frequency rotary mechanical alternator from the General Electric Company capable of generate AC at a frequency of 100 kHz to be used for continuous wave radio transmission over great distances. The design job was given to General Electric engineer Ernst F. Alexanderson who developed the 2 kW Alexanderson alternator. By 1916 Alexanderson added a magnetic amplifier to control the transmission of these rotary alternators for transoceanic radio communication.