Page 4 - The Light Bridge and TESLA's Apparition
P. 4

Bell’s Photophone (1880)








           You may know that a telephone uses electricity to send voice communications.
           However, you may not know that the man who invented the telephone,                                           Illustration of a photophone transmitter,
                                                                                                                         showing the path of reflected sunlight,
           Alexander Graham Bell (1847-1922) had another invention that used light to                                         before and after being modulated.

           transmit sound. He called it the photophone.

           Imagine a solar-powered telephone, and you're close to understanding the
           important gadget Alexander Graham Bell invented on June 3, 1880, four years

           after he had patented the telephone. Bell considered the photophone one of
           his most important inventions. He's probably right, since the technology

           behind the photophone led to the technology that helps computers send
           information around the world today.


           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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