File:Vacuum tube push-pull amplifier 1924.jpg
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Summary
| Description |
English: An early vacuum tube audio amplifier from 1924, used to amplify the output of a low power radio receiver designed for earphones, to give it enough power to drive a loudspeaker. It is a 3 tube "push-pull" circuit, with the first tube (left) operating class A providing the power to drive two output tubes class B in opposite phase through a center tapped transformer. The vacuum tubes were early directly heated triodes, the article says either UV199, 201A or 301A tubes could be used. The amplifier was powered by batteries connected to the binding posts at top: it required 6V for the filaments of the tubes, 60-120V for the plate supply, and a third bias voltage of 6-9V. |
| Date | |
| Source | Retrieved November 4, 2015 from "Push-pull amplifiers" in Radio in the Home magazine, Henry M Neely Publishing Co., Philadelphia, PA, Vol. 2, No. 10, March 1924, p. 12 on www.americanradiohistory.com |
| Author | Unknown author |
| Permission (Reusing this file) |
This 1924 issue of Radio in the Home magazine would have the copyright renewed in 1952. 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 1951, 1952 and 1953 show no renewal entries for Radio in the Home. Therefore the magazine's 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 | 07:19, 4 February 2018 | | 646 × 226 (33 KB) | Chetvorno | User created page with UploadWizard |
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