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the photophone
The Photophone, also known as a radiophone, was invented jointly by Alexander Graham Bell
He said it was his greatest invention.
It is a means of communication...through the transmission of light.
He invented the telephone, the photophone, and the original audiometer.
A photophone is used to allow speech into a light beam. The invention was released in Feb. 19th, 1880 by Alexander Graham Bell.
Very little, even today people do not really use videophones very often, even if their phones have the facility.