Pair of early Bell telephones, 1878.

UNITED STATES - JUNE 25: After experimenting with various acoustical devices, Bell (1847-1922) produced the first intelligible telephonic transmission with a message to his assistant on 5 June 1875. He patented this device as the telephone in 1876, a patent he had to defend against Elisha Gray. Bell, who became a naturalised American in 1874, also invented the phonograph (1880) and the gramophone (1887). Among Bell�s other achievements was the photophone which transmitted sound on a beam of light - a precursor of today�s optical fibre systems, and the invention of techniques for teaching speech to the deaf. (Photo by SSPL/Getty Images)