File:Horn loudspeaker truck 1929.jpg
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| Description |
English: A prototype horn loudspeaker driven by compressed air and an "artificial larynx" used as a portable public address system in Los Angeles, California, USA in 1929. The inventors tried to imitate human vocal cords. It could reportedly project voice or recorded music 4 miles. A vacuum tube audio amplifier powered 4 "artificial larynxes" which modulated compressed air going into the horn provided by a 50 HP gasoline engine and compressor. The owners rented out the powerful system for $300 per hour. Caption: The external appearance of the truck carrying the speaker. A portion of the powerful system - generators and compressors - may be seen alongside the horn. |
| Date | |
| Source | Retrieved July 10, 2014 from C. Sterling Gleason, "Giant Speaker of Four Mile Range" in Radio News magazine, Experimenter Publishing Co., Inc., New York, Vol. 10, No. 11, May 1929, p. 987 archived on American Radio History website |
| Author | C. Sterling Gleason |
| Permission (Reusing this file) |
This 1929 issue of Radio News magazine would have the copyright renewed in 1957. 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 1956, 1957 and 1958 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 | 04:33, 4 October 2014 | | 731 × 493 (53 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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