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CCIR System I is an analog broadcast television system. It was first used in the Republic of Ireland starting in 1962 as the 625-line broadcasting standard to be used on VHF Band I and Band III, sharing Band III with 405-line System A signals radiated in the north of the country. The UK started its own 625-line television service in 1964 also using System I, but on UHF only - the UK has never used VHF for 625-line television. Since then, System I has been adopted for use by Hong Kong, Macau, the Falkland Islands and South Africa. The Republic of Ireland has (slowly) extended its use of System I onto the UHF bands. As of late 2012, analog television is no longer transmitted in either the UK or the Republic of Ireland. South Africa expects to discontinue System I in 2013, and Hong Kong by 2015. == Specifications == Some of the important specs are listed below.〔Reference Data for Radio Engineers, ITT Howard W.Sams Co., New York, 1977, section 30〕 A frame is the total picture. The frame rate is the number of pictures displayed in one second. But each frame is actually scanned twice interleaving odd and even lines. Each scan is known as a field (odd and even fields.) So field rate is twice the frame rate. In each frame there are 625 lines (or 312.5 lines in a field.) So line rate (line frequency) is 625 times the frame frequency or 625•25=15625 Hz. The total RF bandwidth of System I (as originally designed with its single FM audio subcarrier) was about 7.4 MHz, allowing System I signals to be transmitted in 8.0 MHz wide channels with an ample 600 kHz guard zone between channels. In specs, sometimes, other parameters such as vestigial sideband characteristics and gamma of display device are also given. 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「CCIR System I」の詳細全文を読む スポンサード リンク
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