File:Farrand early cone speaker 1929.jpg
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| Description |
English: Drawing of an early cone loudspeaker, the "Farrand Inductor" by Acoustical Engineering Associates, New York, from an advertisement in a 1929 radio magazine. Loudspeakers that used a paper cone for a diaphragm replaced horn loudspeakers in the mid-1920s. Although many cone speakers from this time used older moving-iron drivers, this one used the "electrodynamic" moving coil mechanism invented in 1924 by Chester Rice and Edward Kellogg, and so worked similarly to a modern speaker. The two horseshoe magnets that generated the magnetic field are visible. It was sold in two sizes: the 10" model 6-G for $10 and the 12" Model 10-G for $11. Part of ad copy: "An entirely new principle is involved in the Inductor unit. The armature, instead of moving from side to side in the direction of the pole pieces, as happens in the ordinary magnetic units, moves like a piston along the length of the air gap and maintains a steady distance from the pole pieces. As the sensitivity is extraordinarily high, the gap is made wide and the armature will not strike the pole pieces." |
| Date | |
| Source | Retrieved March 5, 2014 from Radio World magazine, Hennessey Radio Publications Corp., New York, Vol. 16, No. 11, November 30, 1929, p. 4 on American Radio History website. |
| Author | Unknown author |
| Permission (Reusing this file) |
This 1929 issue of Radio World 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 World. Therefore the magazine's 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 | 08:53, 7 March 2014 | | 367 × 445 (29 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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