by BD Mitchell
One hundred facts that are interesting but ultimately useless.
- history / technology -
The photophone -- invented in 1880 by Alexander Graham Bell and Charles Sumner Tainter -- was the first operational wireless telephone. Predating radio transmitting by nearly twenty years, the photophone worked by linking a microphone to a focused beam of sunlight; when sound waves interacted with the microphone, the light beam would become interrupted and modulated. The modulated light could then be transmitted to a separate receiver containing a light-reactive selenium cell, which converted the beam back to sound waves.
In one experiment, Bell and his assistant transmitted clearly over a distance of nearly seven-hundred feet (over two-hundred meters).
With numerous technological limitations at the time -- including interference by weather and the requirement of direct line-of-sight -- the photophone was largely neglected in favor of radio telegraphs.
Despite the technology's shortcomings, the photophone is often cited as Bell's favorite invention -- so much so that it was nearly the namesake of his second daughter.