   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 , tÄle, "far" and ÏÏÎ½Î®, phÅnÄ, "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 rapidly became 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 until approximately the 1970s most telephones used a rotary dial, which was superseded by the modern dtmf push-button dial, first introduced by at&t in 1963.dodd, annabel z., the essential guide to telecommunications. prentice hall ptr, 2002, p. 183. 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. the transmitter converts the sound waves to electrical signals which are sent through the telephone network to the receiving phone. the receiving telephone converts the signals into audible sound in the receiver, or sometimes a loudspeaker. telephones are a duplex communications medium, meaning they allow the people on both ends to talk simultaneously. a landline telephone is connected by a pair of wires to the telephone network, while a mobile phone, such as a cellular phone, is portable and communicates with the telephone network by radio transmissions. the public switched telephone network, consisting of telephone lines, fiberoptic cables, microwave transmission, cellular networks, [[communi
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