Audion

The Audion was one the first electronic devices able to increase sounds. It was invented by American inventor Lee de Forest in 1906.De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers the Audion is , Space Telegraphy, filed January 29, 1907, issued February 18, 1908 The link is to a reprint of the paper in the Scientific American Supplement, Nos. 1665 and 1666, November 30, 1907 and December 7, 1907, p.348-350 and 354-356. It was a glass tube with no air inside. It contained three parts: a filament, a plate, and a grid. 

It was the first functional electronic amplifier. It replaced older technologies, such as the coherer used in early radios. It enabled live radio broadcasting for the first time. Non-paywalled reprint of the DeForest presentation at the October 26, 1906 New York meeting of the AIEE. Text version available at the Early Radio History site.

References

Other websites

 1906 photograph of the original Audion tube, from New York Public Library Digital Gallery

Category:Electronics