A telephone is a communication device that allows two or more users to hold a conversation when they are too far away to be easily heard directly. A phone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cable or other communication channels to another phone that reproduces the sound to the receiving user.


In 1876, Alexander Graham Bell became the first person to receive a United States patent for a device that replicated the human voice in a clearly intelligible manner on a second device. This tool was further developed by others and quickly became indispensable in business, government and homes.
Early telephones connected directly from one customer's office or home to another customer's location. After a few customers, these systems, which proved impractical, were replaced with centrally located panels that were quickly operated manually. These exchanges were soon interconnected, eventually creating an automated, worldwide public switched telephone network. For greater mobility, various radio systems for transmission between mobile stations on ships and automobiles were developed in the mid-20th century. Hand-held mobile phones were introduced for personal service starting in 1973. In later years, analog cellular systems evolved into lower-cost and higher-capacity digital networks.

Digital phones and voice over IP

IP desk phone connected to a computer network

The invention of the transistor in 1947 significantly changed the technology used in telephone systems and long- and short-distance transmission networks over the next several decades. With the development of stored program control and MOS integrated circuits for electronic switching systems and new transmission technologies such as pulse code modulation (PCM), telephony gradually evolved towards digital telephony, which increased the capacity, quality and cost of the network.

The Integrated Services Digital Network (ISDN) was launched in the 1980s, providing businesses and consumers with access to digital telephony services such as data, voice, video and fax services.

The development of digital data communications solutions enabled voice to be digitized and transmitted as simultaneous data over computer networks and the Internet, giving rise to the field of Internet Protocol (IP) telephony, also known as Voice over Internet Protocol (VoIP). ). VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone network infrastructure.

Wireless Phones

A cordless telephone system consisting of a base station and a handset resting on it and a second handset resting on a battery charging unit

A cordless phone or portable phone consists of a base station unit and one or more portable wireless handsets. The base station connects to a phone line or provides voice over IP (VOIP) service. The handset communicates with the base station via radio frequency signals. The operating range of a handset is usually limited within the same building or within a certain distance from the base station.

Base station

Base stations contain a radio transceiver that provides bilateral, outgoing and incoming signals and conversation with handheld terminals. The base station usually includes a microphone, audio amplifier, and speaker for hands-free calls without the need to use a handset.

Telephone networks, which were initially established in cities, later turned into intercity and international systems, and communication between all parts of the world was ensured through satellites.

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