In 1880 he invented the photophone, which transmitted speech via light waves
It was invented jointly by Alexander 
Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at 
Bell's ... Of the 18 patents granted in Bell's name alone, and the 12 he shared 
with his... [DOC] [TLE] How Alexander Graham Bell Pioneered Li-Fi With the Photophone ... [PAR] Dec 28, 2015 ... Functionally, wires limited the use of Bell's invention: The major example of this ...