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A rotary dial telephone, c. 1940s
AT&T push button telephone made by Western Electric, model 2500 DMG black, 1980

A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from Greek: τῆλε (tēle, far) and φωνή (phōnē, voice), together meaning distant voice. A common short form of the term is phone, which came into use almost immediately after the first patent was issued.[1]

In 1876, Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice at a second device.[2] This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households.

The essential elements of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) which reproduces the voice in a distant location.[3] In addition, most telephones contain a ringer to announce an incoming telephone call, and a dial or keypad to enter a telephone number when initiating a call to another telephone. 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 a telephone network to the receiving telephone, which converts the signals into audible sound in the receiver or sometimes a loudspeaker. Telephones ar

A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from Greek: τῆλε (tēle, far) and φωνή (phōnē, voice), together meaning distant voice. A common short form of the term is phone, which came into use almost immediately after the first patent was issued.[1]

In 1876, Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice at a second device.[2] This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households.

The essential elements of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) which reproduces the voice in a distant location.[3] In addition, most telephones contain a ringer to announce an incoming telephone call, and a dial or keypad to enter a telephone number when initiating a call to another telephone. 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 a telephone network to the receiving telephone, which converts the signals into audible sound in the receiver or sometimes a loudspeaker. Telephones are duplex devices, meaning they permit transmission in both directions simultaneously.

The first telephones were directly connected to each other from one customer's office or residence to another customer's location. Being impractical beyond just a few customers, these systems were quickly replaced by manually operated centrally located switchboards. These exchanges were soon connected together, eventually forming an automated, worldwide public switched telephone network. For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the mid-20th century. Hand-held mobile phones were introduced for personal service starting in 1973. In later decades their analog cellular system evolved into digital networks with greater capability and lower cost.

Convergence has given most modern cell phones capabilities far beyond simple voice conversation. Most are smartphones, integrating all mobile communication and many computing needs.

  • One type of mobile phone, called a cell phone

  • Digital telephones and voice over IP

    transistor in 1947 dramatically changed the technology used in telephone systems and in the long-distance transmission networks, over the next several decades. Along with the development of stored program control for electronic switching systems, and new transmission technologies, such as pulse-code modulation (PCM), telephony gradually evolved towards digital telephony, which improved the capacity, quality, and cost of the network.[18]

    The development of digital data communications methods made it possible to digitize voice and transmit it as real-time data across computer networks and the Internet, giving rise to the field of Internet Protocol (IP) telephony, also known as voice over Internet Protocol (VoIP), a term that reflects the methodology memorably. VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone network infrastructure.

    By January 2005, up to 10% of telephone subscribers in Japan and South Korea had switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing."[19] The technology has spawned a new industry comprising many VoIP companies that offer services to consumers and businesses.

    IP telephony uses high-bandwidth Internet connections and specialized customer premises equipment to transmit telephone calls via the Internet, or any modern private data network. The customer equipment may be an analog telephone adapter (ATA) which translates the signals of a conventional analog telephone to packet-switched IP messages. IP Phones have these function combined in standalone device, and computer softphone applications use microphone and headset devices of a personal computer.

    While traditional analog telephones are typically powered from the central office through the telephone line, digital telephones require a local power supply. Internet-based digital service also requires special provisions to provide the service location to the emergency services when an The development of digital data communications methods made it possible to digitize voice and transmit it as real-time data across computer networks and the Internet, giving rise to the field of Internet Protocol (IP) telephony, also known as voice over Internet Protocol (VoIP), a term that reflects the methodology memorably. VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone network infrastructure.

    By January 2005, up to 10% of telephone subscribers in Japan and South Korea had switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing."[19] The technology has spawned a new industry comprising many VoIP companies that offer services to consumers and businesses.

    IP telephony uses high-bandwidth Internet connections and specialized customer premises equipment to transmit telephone calls via the Internet, or any modern private data network. The customer equipment may be an analog telephone adapter (ATA) which translates the signals of a conventional analog telephone to packet-switched IP messages. IP Phones have these function combined in standalone device, and computer softphone applications use microphone and headset devices of a personal computer.

    While traditional analog telephones are typically powered from the central office through the telephone line, digital telephones require a local power supply. Internet-based digital service also requires special provisions to provide the service location to the emergency services when an emergency telephone number is called.

    In 2002, only 10% of the world's population used mobile phones and by 2005 that percentage had risen to 46%.[20] By the end of 2009, there were a total of nearly 6 billion mobile and fixed-line telephone subscribers worldwide. This included 1.26 billion fixed-line subscribers and 4.6 billion mobile subscribers.[21]

    Characteristi

    The Unicode system provides various code points for graphic symbols used in designating telephone devices, services, or information, for print, signage, and other media.

    • U+2121 TELEPHONE SIGN
    • U+260E BLACK TELEPHONE
    • U+260F