Humanities › History & Culture Alexander Graham Bell's Photophone Was An Invention Ahead of Its Time While the telephone used electricity, the photophone used light Share Flipboard Email Print Apic / Hulton Archive / Getty Images History & Culture Inventions Famous Inventions Famous Inventors Patents & Trademarks Invention Timelines Computers & The Internet American History African American History African History Ancient History and Culture Asian History European History Genealogy Latin American History Medieval & Renaissance History Military History The 20th Century Women's History View More By Mary Bellis Inventions Expert Mary Bellis covered inventions and inventors for ThoughtCo for 18 years. She is known for her independent films and documentaries, including one about Alexander Graham Bell. our editorial process Mary Bellis Updated March 07, 2019 While he's best known as the inventor of the telephone, Alexander Graham Bell considered the photophone his most important invention... and he may have been right. On June 3, 1880, Alexander Graham Bell transmitted the first wireless telephone message on his newly invented "photophone," a device that allowed for the transmission of sound on a beam of light. Bell held four patents for the photophone and built it with the help of an assistant, Charles Sumner Tainter. The first wireless voice transmission took place over a distance of 700 feet. How It Worked Bell's photophone worked by projecting voice through an instrument toward a mirror. Vibrations in the voice caused oscillations in the shape of the mirror. Bell directed sunlight into the mirror, which captured and projected the mirror's oscillations toward a receiving mirror, where the signals were transformed back into sound at the receiving end of the projection. The photophone functioned similarly to the telephone, except the photophone used light as a means of projecting the information, while the telephone relied on electricity. The photophone was the first wireless communications device, preceding the invention of the radio by nearly 20 years. Although the photophone was an extremely important invention, the significance of Bell's work was not fully recognized in its time. This was largely due to practical limitations in the technology of the time: Bell's original photophone failed to protect transmissions from outside interferences, such as clouds, that easily disrupted transport. That changed nearly a century later when the invention of fiber optics in the 1970s allowed for the secure transport of light. Indeed, Bell's photophone is recognized as the progenitor of the modern fiber optic telecommunications system that is widely used to transmit telephone, cable, and internet signals across large distances.