File:Arnold mercury-arc amplifier 1912.jpg
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Summary
| Description |
English: An experimental mercury arc vacuum tube developed as an amplifying repeater for telephone lines around 1912 by Harold D. Arnold at Western Electric the manufacturing arm of the Bell Telephone Company. This is one of several crude technologies which telephone companies used to amplify telephone signals before the adoption of the Audion (triode) vacuum tube in 1913, and is notable chiefly as an amplifier tube that predated the vacuum tube. Arnold's tube amplified adequately, but was so difficult to adjust that it was only used briefly in one long distance line. The tube functioned by negative resistance cancelling the positive resistance of the telephone line, so it had to be adjusted carefully to the individual resistance of each line, or it would oscillate, producing shrieks and whistles on the line. |
| Date | |
| Source | Retrieved April 7, 2015 from Gerald F. J. Tyne, "The Saga of the Vacuum Tube" in Radio News magazine, Ziff-Davis Publishing Co., Chicago, IL, Vol. 30, No. 6, December 1943, p. 30, fig. 61 on http://www.americanradiohistory.com |
| Author | Unknown author |
| Permission (Reusing this file) |
This 1943 issue of Radio News magazine would have the copyright renewed in 1971. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1970, 1971, and 1972 show no renewal entries for Radio News. Therefore the copyright was not renewed and it is in the public domain. |
Licensing
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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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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 01:56, 8 April 2015 | | 400 × 631 (57 KB) | Chetvorno | User created page with UploadWizard |
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