Lee de Forest - Audion

Audion

De Forest was interested in wireless telegraphy and invented the Audion in 1906. He then developed an improved wireless telegraph receiver.

On 25 October 1906, de Forest filed a patent for diode vacuum tube detector, a two-electrode device for detecting electromagnetic waves, a variant of the Fleming valve invented two years earlier. One year later, he filed a patent for a three-electrode device that was a much more sensitive detector of electromagnetic waves. It was granted US Patent 879,532 in February 1908. The device was also called the de Forest valve, and since 1919 has been known as the triode. De Forest's innovation was the insertion of a third electrode, the grid, between the cathode (filament) and the anode (plate) of the previously invented diode. The resulting triode or three-electrode vacuum tube could be used as an amplifier of electrical signals, notably for radio reception. The Audion was the fastest electronic switching element of the time, and was later used in early digital electronics (such as computers). The triode was vital in the development of transcontinental telephone communications, radio, and radar after Nikola Tesla's and Guglielmo Marconi's progress in radio in the 1890s, until the 1948 invention of the transistor.

De Forest had, in fact, stumbled onto this invention via tinkering and did not completely understand how it worked. De Forest had initially claimed that the operation was based on ions created within the gas in the tube when, in fact, it was shown by others to operate with a vacuum in the tube. The device was subsequently carefully investigated by H. D. Arnold and his team at Western Electric (AT&T) and Irving Langmuir at the General Electric Corp. Both of them correctly explained the theory of operation of the device and provided significant improvements in its construction.

In 1904, a De Forest transmitter and receiver were set up aboard the steamboat Haimun operated on behalf of The Times, the first of its kind. On July 18, 1907, De Forest broadcast the first ship-to-shore message from the steam yacht Thelma. The communication provided quick, accurate race results of the Annual Inter-Lakes Yachting Association (I-LYA) Regatta. The message was received by his assistant, Frank E. Butler of Monroeville, Ohio, in the Pavilion at Fox's Dock located on South Bass Island on Lake Erie. DeForest disliked the term "wireless", and chose a new moniker, "radio". De Forest is credited with the birth of public radio broadcasting when on January 12, 1910, he conducted experimental broadcast of part of the live performance of Tosca and, the next day, a performance with the participation of the Italian tenor Enrico Caruso from the stage of Metropolitan Opera House in New York City.

De Forest came to San Francisco in 1910, and worked for the Federal Telegraph Company, which began developing the first global radio communications system in 1912. California Historical Landmark No. 836 is a bronze plaque at the eastern corner of Channing St. and Emerson Ave. in Palo Alto, California, which memorializes the Electronics Research Laboratory at that location and De Forest for the invention of the three-element radio vacuum tube.