File:First Bell telephone 1875.png
First_Bell_telephone_1875.png (453 × 348 pixels, file size: 59 KB, MIME type: image/png)
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DescriptionFirst Bell telephone 1875.png |
English: A model of the first telephone transmitter/receiver (microphone/speaker) invented by US scientist Alexander Graham Bell in 1875. It is now known as the "Gallows" instrument due to its shape. It was the first device through which sounds were transmitted, but could not transmit intelligible speech. Bell designed it after his seminal June 2, 1875 experiment in which he realized that a vibrating metal reed could transmit not only musical tones but the more complicated waveforms of speech, and it was built by his collaborator, Thomas A. Watson. It functioned as both a dynamic microphone and a speaker. Bell found that two of these devices wired in a circuit with a battery functioned as a crude bidirectional telephone; sounds spoken into one would be heard faintly from the other. It took another year of work before intelligible speech could be transmitted. This is probably not the transmitter used in Bell's famous first communication of speech on March 10, 1876: "Come here, Watson, I need you"; Bell had improved electromagnetic transmitter designs by then, and some sources say a liquid transmitter was used on that occasion. It consists of a parchment diaphragm stretched over a cup-shaped sound collector, attached to an iron armature on a springy metal reed, near a pickup coil of wire wound on an iron core attached to the binding posts at top. It was included in Bell's telephone patent of March 7, 1876. This image shows a model of the original device; Thomas A. Watson wrote in 1915 (p. 1017 below) that "all that is left" of the original was in the National Museum in Washington. Information from Thomas A. Watson (May 18, 1915) How Bell invented the telephone, Trans. of the American Inst. of Electrical Engineers, Vol. 34, Part I, p. 1011-1021 |
Date | |
Source | Retrieved October 14, 2014 from Western Electric Oscillator magazine, published by Western Electric Co., New York, NY, No. 7, March 1947, p. 15 on http://www.americanradiohistory.com |
Author | Unknown authorUnknown author |
Permission (Reusing this file) |
This 1947 issue of Oscillator magazine would have the copyright renewed in 1975. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found at The Online Books Page. Search of the Renewals for Periodicals for 1974, 1975, and 1976 show no renewal entries for Oscillator. Therefore the magazine's copyright was not renewed and it is in the public domain. |
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Public domainPublic domainfalsefalse |
This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
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File change date and time | 03:16, 15 October 2014 |