Multichannel television sound

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 analog NTSC-format audio carrier.

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.

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