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Alexander Graham Bell speaking on the telephone in 1892
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Alexander Graham Bell Invented the Photophone
June 3, 1880
Bell's photophone was based on transmitting sound on a beam of light. A person's voice was projected through an instrument toward a mirror. The vibrations of the voice caused similar vibrations in the mirror. Sunlight was then directed into the mirror, where the vibrations were captured and projected back to the photophone's receiver. There they were converted back into sound.It took a long time before the idea behind Bell's photophone became practical. The original machine had a big flaw: when the weather was cloudy it didn't work! Today, digital voice and data communications are transmitted at the speed of light through glass fibers called optical fiber.
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