Telephone

—An instrument for the electrical transmi ion of articulate sound to long distances. One speaks into a transmitter, the sound vibrations of the voice causing a thin sheet metal or carbon disc to vibrate, causing electric waves to be set up in a steel magnet behind the disc. The electric waves are transmitted through the magnet winding to the conducting line, along the latter to the receiver, which is similar in construction to the transmitter, and, setting up, corresponding vibrations in the disc of the receiver, make the sounds audible at the farend. The return current is through the earth.