A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are not in the same vicinity of each other to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals suitable for transmission via cables or other transmission media over long distances, and replays such signals simultaneously in audible form to its user. The word telephone has been adapted into the vocabulary of many languages. It is derived from the Greek: τῆλε, tēle, far and φωνή, phōnē, voice, together meaning distant voice.
First patented in 1876 by Alexander Graham Bell and further developed by many others, the telephone was the first device in history that enabled people to talk directly with each other across large distances. Telephones became rapidly indispensable to businesses, government, and households, and are today some of the most widely used small appliances.
The essential elements of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) which reproduces the voice of the distant person. In addition, most telephones contain a ringer which produces a sound to announce an incoming telephone call, and a dial used to enter a telephone number when initiating a call to another telephone. Until approximately the 1970s most telephones used a rotary dial, which was superseded by the modern Touch-Tone push-button dial, first introduced by AT&T in 1963. The receiver and transmitter are usually built into a handset which is held up to the ear and mouth during conversation. The dial may be located either on the handset, or on a base unit to which the handset is connected by a cord containing wires.
The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send electrical pulses, known as pulse dialing, corresponding to the number dialed. The early form of the rotary dial used lugs on a finger plate instead of holes. Almon Brown Strowger filed the first patent for a rotary dial, U.S. patent #486,909, on December 21, 1891, that was later issued to him on November 29, 1892.
The modern version of the rotary dial with holes was first introduced in 1904 but did not enter service in the Bell System until 1919. The rotary dial was gradually supplanted by Dual-tone multi-frequency pushbutton dialing, introduced at the 1962 World's Fair, which uses a keypad instead of a dial. Some telephone systems in the US no longer recognize pulse dialing by default, but will only support tone dialing which is usually used with push-button phones. (though rotary dial phones with tone dialing support do exist).