Photophone

The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented by Alexander Graham Bell along with his assistant Charles Sumner Tainter on February 19, 1880. Bell believed that the photophone was his most important invention.

Photophone Media

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  A historical plaque on the side of the Franklin School in Washington, D.C. which marks one of the points from which the photophone was demonstrated

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  A diagram from one of Bell's 1880 papers

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  A photophone receiver and headset, one half of Bell and Tainter's optical telecommunication system of 1880

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  Illustration of a photophone transmitter, showing the path of reflected sunlight, before and after being modulated

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  Illustration of a photophone receiver, depicting the conversion of modulated light to sound, as well as its electrical power source (P)

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  Ernst Ruhmer at his "photo-electric" optical telephone system station. (1905)