File:Shreeve carbon telephone repeaters AT&T Providence RI 1919.jpg
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Summary
| Description |
English: Shreeve carbon telephone line repeaters for AT&T Boston-to-Washington DC long distance trunkline in Providence, RI switching center, 1919. These devices, invented in 1903 by Herbert Shreeve at Western Electric, consisted of a small speaker coupled to a carbon microphone. They were some of the earliest electronic amplifiers, used for a short period before Audion (triode) vacuum tube repeaters superseded them around 1920. Each identical vertical panel contains the repeaters and support equipment for one wire in the trunkline. The repeaters are the canlike cylindrical objects projecting from the panel in a double row along the top. Each bidirectional line required two repeaters, one for each direction. Below the repeaters are rheostats for adjusting the DC current on the line, and power supply for the repeaters. These electromechanical devices were very unsatisfactory as amplifiers. The mass of the acoustic driver gave them a sharp resonance peak that emphasized certain audio frequencies. They suffered from DC offset due to temperature drift, and "carbon hiss", electronic noise generated by the carbon granules in the microphone that sounded like a roaring in the background. |
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| Source | Retrieved October 19, 2015 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 55, fig. 47, following p.1342 on Google Books |
| Author | Bancroft Gherardi and Frank B. Jewett |
Licensing
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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 | |
|---|---|---|---|---|---|
| current | 09:11, 20 July 2015 | | 1,295 × 1,612 (360 KB) | Chetvorno | User created page with UploadWizard |
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