Multichannel television sound
Multichannel television sound, better known as MTS or BTSC, is the method of encoding three additional channels of audio onto an NTSC-format video signal. It was adopted by the FCC as the U.S. standard for stereo television transmission in 1984.
The first channel is the stereo difference (left minus right), used to add stereophonic sound to the existing monophonic (the left plus right stereo sum) audio track. The stereo information is DBX-encoded to increase the signal-to-noise ratio, to aid in noise reduction.
The second audio program (SAP) also is part of the standard, providing another language, a video description service like DVS, or a completely separate service like a campus radio station or weatheradio.
A third PRO (professional) channel is provided for internal use by the station, and may handle audio or data. It is normally used with electronic news gathering during news broadcasts to talk to the remote location (such as a reporter on-location), which can then talk back through the remote link to the TV station. Receivers for this channel may not be sold to the public.
