File:Edwin Armstrong & portable superheterodyne.jpg
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Summary[edit]
| Description |
English: US engineer Edwin Armstrong at beach with a portable superheterodyne radio receiver he built for his wife. Armstrong invented the superheterodyne, the circuit used in virtually all modern receivers, in 1918 during World War 1 when he was a major in the US Signal Corps. |
| Date | |
| Source | Retrieved July 4, 2014 from Radio News magazine, Experimenter Publications, Inc., New York, Vol. 5, No. 10, April 1924, p. 1405 archived on American Radio History website |
| Author | Unknown author |
| Permission (Reusing this file) |
This 1924 issue of Radio News 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. [1] Search of the Renewals for Periodicals for 1951, 1952 and 1953 show no renewal entries for Radio News. Therefore the copyright was not renewed and it is in the public domain. |
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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 | 23:15, 4 August 2014 | | 409 × 771 (68 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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