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Multichannel television sound, better known as MTS (often still as BTSC, for the Broadcast Television Systems Committee that created it), is the method of encoding three additional channels of audio into an NTSC-format audio carrier. == History == Multichannel Television Sound was adopted by the Federal Communications Commission as the U.S. standard for stereo television transmission in 1984. Initial work on design and testing of a stereophonic audio system began in 1975 when Telesonics approached Chicago public television station WTTW. WTTW was producing a music show titled ''Soundstage'' at that time, and was simulcasting the stereo audio mix on local FM stations. Telesonics and WTTW formed a working relationship and began developing the system which was similar to FM stereo modulation. Twelve WTTW studio and transmitter engineers added the needed broadcast experience to the relationship. The Telesonics system was tested and refined using the WTTW transmitter facilities on the Sears Tower. In 1979, WTTW had installed a stereo Grass Valley master control switcher, and had added a second audio channel to the microwave STL (Studio Transmitter Link). By that time, WTTW engineers had further developed stereo audio on videotape recorders in their plant, using split audio track heads manufactured to their specifications, outboard record electronics, and Dolby noise reduction that allowed ''Soundstage'' to be recorded and electronically edited. In addition, an Ampex MM1100, 24-track audio recorder was also used for music production and mixing. PBS member stations who wished to deliver ''Soundstage'' in stereo were provided with a four-track (left, right, vertical drive, and time code) audio tape that could be synced with the video machines in those cities. During the FCC approval process, several manufacturers applied to the FCC for consideration. Most notably the Electronic Industries Alliance (EIA) and Japanese EIA asked to be included in order to represent their members in the testing and specification phases of the approval process. WTTW engineers helped set standards for frequency response, separation, and other uses of the spectrum. They also provided program source material used for the testing and maintained the broadcast chain. A 3M 24-track audio recorder was used to allow the selection of 12 different stereo programs for testing. The Matsushita Quasar TV manufacturing plant and laboratory, just west of Chicago, was used as the source for all testing of the competing systems. Following the testing, several questions were raised about the validity of some of the tests, and a second round of testing began. WTTW installed a Broadcast Electronics prototype stereo modulator in October 1983, and began full-time broadcasting in stereo at that time using the Telesonics system prior to FCC rule-making on the BTSC system. Following EIA and FCC recommendations, the BE modulator was modified to meet BTSC specifications, and by August 1984 was in full-time use on WTTW. Sporadic network transmission of stereo audio began on NBC on July 26, 1984, with ''The Tonight Show Starring Johnny Carson'', although at the time only the network's New York City flagship station, WNBC, had stereo broadcast capability;〔Peter W. Kaplan, "TV Notes", ''New York Times'', July 28, 1984, sec. 1, p. 46.〕 regular stereo transmission of NBC programs began during early 1985. ABC and CBS followed suit in 1986 and 1987, respectively. FOX was the last network to join around 1990, with the four networks having their entire prime-time schedules in stereo by late 1994 (The WB and UPN, launched the following season with their entire line-ups in stereo). One of the first television receiving systems to include BTSC capability was the RCA Dimensia, released in 1984. 〔(RCA Dimensia FKC2600E and FKC2601T Monitors ). Cedmagic.com. Retrieved on 2014-05-11.〕 From the mid-1980s to the mid-1990s and also in the 2000s, the networks would display the disclaimer "In stereo (where available)" at the beginning of stereo programming. 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「Multichannel television sound」の詳細全文を読む スポンサード リンク
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