File:Lee De Forest and Audion transmitter.jpg
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English: American electrical engineer Lee De Forest, inventor of the Audion (triode) vacuum tube, and one of the first AM radio transmitters, from around 1920. The Audion made practical amplitude modulation (AM or audio) transmitters possible, and was responsible for the rise of radio broadcasting around 1920. The box on the left is the transmitter, the one on the right is a receiver. The Audion vacuum tubes are visible mounted on the front of the device. De Forest is speaking into a telephone-type carbon microphone, which was connected directly in the antenna lead to modulate the radio carrier. The caption read: "Dr. De Forest trying out one of his recent inventions, a portable wireless telephone operated entirely by current from a lamp socket." Most early radios operated from batteries; this one had an internal rectifier to allow it to operate from the AC wall current. |
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| Source | Retrieved 28 November 2013 from Lee De Forest, "A Review of Radio" in Radio Broadcast, Doubleday Page and Co., New York, Vol. 1, No. 4, August 1922, p. 337 on Google Books |
| Author | Lee De Forest |
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This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
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This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the rule of the shorter term for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See Wikipedia:Public domain and Wikipedia:Copyrights for more details.
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 20:10, 28 November 2013 | | 844 × 1,168 (173 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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