File:Early Audion telephone repeaters.jpg
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English: Some of the earliest vacuum tube telephone repeaters in 1919, using the Audion triode which Western Electric had licensed from Lee De Forest in 1913. These are in a repeater building in Princeton, New Jersey on a 225 mile trunk line from Boston to Washington DC. Each rack contains two Type 22 repeaters, each consisting of two simple triode amplifiers, one for each direction of the duplex open wire line. The inputs and outputs were transformer-coupled with a bridge arrangement into each side of the line, which was terminated with a matching termination to prevent reflections. The potentiometers (knobs) controlled the grid bias of each tube. The building contains 200 repeaters. At the time of this article only 1000 repeaters were in use in the entire US Bell System. The Audion, the first amplifying vacuum tube, invented in 1906 by Lee De Forest, made transcontinental long distance telephone lines possible. Before the vacuum tube, telephone lines were limited to a few hundred miles. Western Electric purchased the rights to the Audion from De Forest in 1913 and redesigned the tube, improving evacuation and creating the first "hard vacuum" triodes. The first US transcontinental telephone line was opened in 1915, with three repeaters at Pittsburgh, Omaha, and Salt Lake City. |
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| Source | Retrieved 14 October 2013 from Bancroft Gherardi, Frank B. Jewett, "Telephone repeaters" in Trans. of the AIEE (American Institute of Electrical Engineers, New York), Vol. 38, Part 2, 1 October 1919, plate 52, fig. 44, following p.1342 on Google Books |
| Author | Bancroft Gherardi |
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This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
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| current | 16:08, 19 October 2013 | | 968 × 740 (144 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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