Second audio program (SAP), also known as secondary audio programming, is an auxiliary
audio channel
An audio signal is a representation of sound, typically using either a changing level of electrical voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric poten ...
for
analog television
Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, instantaneous phase and frequency, ...
that can be
broadcast
Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum ( radio waves), in a one-to-many model. Broadcasting began ...
or transmitted both
over-the-air and by
cable television
Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with broa ...
. Used mostly for audio description or other languages, SAP is part of the
multichannel television sound
Multichannel Television Sound, better known as MTS, is the method of encoding three additional audio channels into an analog NTSC-format audio carrier. It was developed by the Broadcast Television Systems Committee, an industry group, and somet ...
(MTS) standard originally set by the National Television Systems Committee (
NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
) in 1984 in the United States. The NTSC
video format
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...
and MTS are also used in
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-la