Photophone

The photophone (also known as a radiophone) is a telecommunications device which allowed for the transmission of both articulated sounds and normal human conversations on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D.C. Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell.