Monday, October 12, 2009

The First Tube


De Forest Audion from 1906.De Forest had an interest in wireless telegraphy and he invented the Audion in 1906. He then developed an improved wireless telegraph receiver. At that time, he was a member of the faculty at the Armour Institute of Technology, now part of the Illinois Institute of Technology.

In January 1907, De Forest filed a patent for a two-electrode device for detecting electromagnetic waves, a variant of the Fleming valve invented two years earlier, a.k.a. the diode vacuum tube detector. It was granted US Patent 879,532 in February 1908. It was a three-electrode device (plate, cathode, control grid), was a vacuum tube. It 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, in 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 for electrical signals, notably for radio reception. The Audion could also act as a fast (for its time) electronic switching element, later applicable in digital electronics (such as computers). The triode was vital in the development of long-distance (e.g. transcontinental) telephone communications, radio, and radar. The triode was an important innovation in electronics in the first half of the 20th century, between Nikola Tesla's and Guglielmo Marconi's progress in radio in the 1890s, and the 1948 invention of the transistor.

De Forest had, in effect, 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 American inventor Irving Langmuir of General Electric Corp. was the first to correctly explain the theory of operation of the device, and also to significantly improve it.

First broadcastIn 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. [3] 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.[4] [5].

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