The
photophone (later given the alternate name
radiophone) is a
telecommunications device which allowed for the
transmission of speech 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.