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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.〔McGraw-Hill Concise Encyclopedia of Engineering. (Videotelephony ), McGraw-Hill, 2002. Retrieved from the FreeDictionary.com website, January 9, 2010〕 At the dawn of the technology, 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. Currently videotelephony usage has made significant inroads in government, healthcare, education and the news media. It is particularly useful to the deaf and speech-impaired who can use the technology with sign language and also with a video relay service, and well as to those with mobility issues or those who are located in distant places and are in need of telemedical or tele-educational services. It is also used in commercial and corporate settings to facilitate meetings and conferences, typically between parties that already have established relationships. Like all long distance communications technologies (such as phone and internet), by reducing the need to travel to bring people together the technology also contributes to reductions in carbon emissions, thereby helping to reduce global warming.〔Coroama, V.C., et al. (Effects of Internet-Based Multiple-Site Conferences on Greenhouse Gas Emissions ), Telemat. Informat. (2011), 〕〔Biello, David. (Can Videoconferencing Replace Travel? ), Scientific American, March 18, 2009.〕〔Pachner, Joanna. (The Next Best Thing to Being There ), Toronto: The Globe and Mail, October 13, 2009.〕 == History == (詳細はvideo telephone, or videophone, and it evolved from intensive research and experimentation in several telecommunication fields, notably electrical telegraphy, telephony, radio, and television. The development of the crucial video technology first started in the latter half of the 1920s in the United Kingdom and the United States, spurred notably by John Logie Baird and AT&T's Bell Labs. This occurred in part, at least with AT&T, to serve as an adjunct supplementing the use of the telephone. A number of organizations believed that videotelephony would be superior to plain voice communications. However video technology was to be deployed in analog television broadcasting long before it could become practical—or popular—for videophones. Videotelephony developed in parallel with conventional voice telephone systems from the mid-to-late 20th century. Very expensive videoconferencing systems rapidly evolved throughout the 1980s and 1990s from proprietary equipment, software and network requirements to standards-based technologies that were readily available to the general public at a reasonable cost. Only in the late 20th century with the advent of powerful video codecs combined with high-speed Internet broadband and ISDN service did videotelephony become a practical technology for regular use. With the rapid improvements and popularity of the Internet, videotelephony has become widespread thru the deployment of video-enabled mobile phones, plus videoconferencing and computer webcams which utilize Internet telephony. In the upper echelons of government, business and commerce, telepresence technology, an advanced form of videoconferencing, has helped reduce the need to travel. The highest ever videocall took place on May 19, 2013 when British adventurer Daniel Hughes used a smartphone with a BGAN satellite modem to make a videocall to the BBC from the summit of Mount Everest, at 8,848 m above sea level.〔Callaham, John. (Man makes the highest Skype video call ever on top of Mount Everest ), Neowin.net website, June 25, 2013; which in turn cites: * Larson, Stephanie. (First Skype Call Atop Mt. Everest Raises Thousands for Charity ), Skype blog, June 24, 2013.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Videotelephony」の詳細全文を読む スポンサード リンク
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