Video telephone

Videotelephony comprises the technologies for the reception and transmission of audio-video signals by users at different locations, for communication between people in real-time. A videophone is a telephone with a video display, capable of simultaneous video and audio for communication between people in real-time. Videoconferencing implies the use of this technology for a group or organizational meeting rather than for individuals, in a videoconference.Telepresence may refer either to a high-quality videotelephony system (where the goal is to create the illusion that remote participants are in the same room) or to meetup technology which goes beyond video into robotics (such as moving around the room or physicially manipulating objects). Videoconferencing has also been called "visual collaboration" and is a type of groupware.

At the dawn of its commercial deployment from the 1950s through the 1990s, videotelephony also included "image phones" which would exchange still images between units every few seconds over conventional POTS-type telephone lines, essentially the same as slow scan TV systems. The development of advanced video codecs, more powerful CPUs, and high-bandwidth in the late 1990s allowed videophones to provide high quality colour service between users almost anyplace in the world that the Internet is available, often at low or nominal costs.

Although not as widely used in everyday communications as audio-only and text communication, useful applications include sign language transmission for deaf and speech-impaired people, distance education, telemedicine, and overcoming mobility issues. It is also used in commercial and corporate settings to facilitate meetings and conferences, typically between parties that already have established relationships. News media have begun to use desktop technologies like Skype to provide higher-quality audio than the phone network, and video links at much lower cost than sending professional equipment or using a professional studio. More popular videotelephony technologies use the Internet rather than the phone network, even accounting for modern digital packetized phone network protocols, and even though videotelephony software commonly runs on smartphones.

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