Early telephone by Alexander Graham Bell, c 1870s.

UNITED KINGDOM - MARCH 12: This box telephone, which was previously used at Lloyds signal station in Crookhaven, represents one of Alexander Graham Bell's (1847-1922) earliest efforts to design a device that would allow long distance communication. Bell's central idea, in this and later designs, was to convert the vibrations of the human voice into electrical signals that could be sent over a wire from one telephone user to another. On 7 March 1876, Bell secured a patent for his invention, and later that year gave a public demonstration of the first telephone at the American Centennial Exhibition in Philadelphia. This design, used for both the transmitter and receiver, became standard when the first telephones were introduced on the market in 1877. (Photo by SSPL/Getty Images)