Telephone

A telephone is a device that converts sound, especially human speech, into electronic signals that travel through a communications network and back into audible sound at the receiving end. The name comes from Greek words meaning far and voice. A working telephone needs a microphone to turn sound into an electrical signal and an earphone to turn the signal back into sound, usually combined into a single handset, along with a ringer or similar alert for incoming calls. Alexander Graham Bell received the first United States patent for an electric telephone able to reproduce intelligible human speech in 1876, though credit for the underlying invention is disputed, with Antonio Meucci, Johann Philipp Reis, Charles Bourseul and Elisha Gray all credited with earlier or parallel contributions. What began as direct point to point connections between individual users grew into automated networks spanning the world, and telephones today take fixed line, cellular, satellite and internet based forms, all reachable through the public switched telephone network by a unique telephone number.