After wired and wireless telegraphy, comes a revolutionary invention that is the possibility of speaking at a distance and making the voice heard at a distance. Something unthinkable before its invention and that completely changed the history of humanity. It is a means of sending sounds through wires. Thanks to the knowledge of radio magnetism and acoustics. Two characters, Antonio MEUCCI (1808-1889) and Alexander Graham BELL (1847-1922), both produced telephone prototypes almost at the same time, and come from researchers with special knowledge of acoustics and electrical telegraphy. The idea was to try to modulate a direct current of electricity, producing small variations in it that could be recorded at the point of reception: James Clerk MAXWELL, creator of the electromagnetic field theory, one of the most important scientists in the history of science , stated that the telephone was not so difficult to imagine.