Today, in my American History class students were discussing Alexander Graham Bell and his invention of the first practical telephone. Quite an achievement it was for the time (mid 1870s). In essence, what Mr. Bell did was find a way to convert speech (voice sound, acoustic energy, sound wave) into electrical signals, transmit those signals via a phone line, and then convert the electrical signals back to speech so that the person on the other end of the line can hear. Way to go, Mr. Bell.
[Photographic Art by Ric Couchman]