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1880 Optical Telephone Transmission Patent

July 3rd Fact-of-the-Day

Alexander Graham Bell and Sumner Tainter were granted a U.S. patent in 1880 for a wireless telephone transmission method they invented where telephone signals are transmitted to a receiving party by means of light propagating through air instead of electric current flowing through wires. Their method involved modulating a light beam by reflecting it off a diaphragm that vibrated in sympathy with sound waves. The angle of the reflected light beam moved from directly toward to slightly away from a light-sensitive receiver as the diaphragm vibrated, causing the received light energy to be amplitude modulated with sound intelligence. They originally called their optical telephone system a 'photophone,' but later changed the name to 'radiophone.' The American Bell Company was granted a patent covering improvements to the method in 1897. Modern fiber optic transmission systems differ in detail, but are closely associated with the Bell and Tainter method in that they both transmit intelligence by means of modulated light energy. ©2005 Martek International All rights reserved.


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