Telephone

Telephone

A 1970's era AT&T "Touch-Tone" telephone
Inventor	Alexander Graham Bell
Launch year	1876
Available?	Worldwide

The telephone , commonly referred to as a phone, is a telecommunications device that transmits and receives sound, most commonly the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to one another. It is one of the most common household appliances in the developed world, and has long been considered indispensable to business, industry and government. The word "telephone" has been adapted to many languages and is widely recognized around the world.

The device uses a microphone in the handset to convert the sound waves to electrical signals, which are sent through the telephone network to the other phone, where they are converted back to sound waves by an earphone in the handset. The telephone network, consisting of a worldwide net of telephone lines, fiberoptic cables, communications satellites, and undersea telephone cables connected by switching centers, allows any telephone in the world to communicate with any other. Each telephone line has an identifying number called its telephone number. In order to initiate a telephone call, a conversation with another telephone, the user enters the other telephone's number into a numeric keypad on his phone. Graphic symbols used to designate telephone service or phone-related information in print, signage, and other media include ℡(U+2121), ☎(U+260E), ☏(U+260F), and ✆(U+2706).