The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880.
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However, sound-on-film systems such as Movietone and RCA Photophone soon became the standard, and sound-on-disc fell into disuse.
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For example, in 1935, the German Army developed a photophone where a tungsten filament lamp with an IR transmitting filter was used as a light source.
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Due to its use of an atmospheric transmission medium, the Photophone would not prove practical until advances in laser and optical fiber technologies permitted the secure transport of light.
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The selenium cell was used in the photophone developed by Alexander Graham Bell in 1879 . Selenium transmits an electric current proportional to the amount of light falling on its surface.
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The Bell Labs'Richard Gundlach and the Smithsonian's Elliot Sivowitch used the device at the commemoration to demonstrate one of the photophone's modern-day descendants.
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The National Geographic Society also mounted a special educational exhibit in its Explorer's Hall, highlighting the photophone's invention with original items borrowed from the Smithsonian Institution.
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The early sound-on-disc processes such as Vitaphone were soon superseded by sound-on-film methods like Fox Movietone, DeForest Phonofilm, and RCA Photophone.
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The release of Alfred Hitchcock's sound feature film " Blackmail " in June 1929, made in RCA Photophone, sealed the fate of Phonofilm in the UK.
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*The Society of Arts issues their second Royal Albert silver medal to him for his paper on his proudest achievement, the Photophone, invented a year earlier ( 1881 );
