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laboratories in 1933. It was demonstrated at the 1933 Chicago World's Fair. During the 1930s the first low power vacuum tubes capable of generating microwaves were invented. The microphone converts the voice of the man into a varying
148:. The microwaves are reflected by the parabolic reflector into a beam, which travels to a receiver several miles away, which converts the electric signal back into sound. The radiated power was about 1 watt.
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539: Note that a few countries have copyright terms longer than 70 years: Mexico has 100 years, Jamaica has 95 years, Colombia has 80 years, and Guatemala and Samoa have 75 years. This image may
288:), 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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magazine would have the copyright renewed in 1961. Online page scans of the
Catalog of Copyright Entries, published by the US Copyright Office can be found
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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
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Uploaded a work by I. E. Mouromtseff from
Retrieved 26 August 2024 from on https://www.worldradiohistory.com with UploadWizard
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implement the rule of the shorter term. Copyright may extend on works created by French who died for France in
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to indicate why this work is in the public domain in the United States.
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the microwaves generated by a small tube at the focus of the shiny
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in its country of origin and other countries and areas where the
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magazine, Popular Book Corp. Vol.4, No.5, September 1933, p.267
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be in the public domain in these countries, which moreover do
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Experimental
Westinghouse 3GHz microwave transmitter 1933.jpg
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Experimental_Westinghouse_3GHz_microwave_transmitter_1933.jpg
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Mouromtseff, I. E. "3.5 inch Waves Now
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
