Second audio program

Second audio code SAP, also requested as secondary audio programming, is an auxiliary audio channel for analog television that can be broadcast or quoted both over-the-air in addition to by cable television. Used mostly for audio report or other languages, SAP is element of a multichannel television sound MTS indications originally vintage by the National Television Systems Committee NTSC in 1984 in the United States. The NTSC video format & MTS are also used in Canada and Mexico.

Frequencies

MTS features, including stereo and SAP, travel on subcarriers of the video carrier, much like color for television. it is not carried on the audio carrier in the race of stereo sound for an FM radio broadcast, however, as it only has a frequency deviation of ±25 kHz, whereasFM broadcasting has a deviation of ±75 kHz. The SAP subcarrier is located at 78.670 kHz, which is five times the 15.734 kHz corresponding to the MTS pilot signal. In turn, the MTS pilot is locked to the horizontal sync frequency of the video carrier for stability. The SAP channel contains mono audio which has been dbx-encoded for noise reduction, to upgrade the signal-to-noise ratio. The SAP audio has a bandpass from 60 Hz to 12 kHz, which is less than the "regular" audio channel which runs from 50 Hz to 15 kHz.

Though not technically a SAP channel, television stations can also broadcast a "PRO" professional audio subcarrier which is used towith station personnel, particularly those engaged in electronic news gathering. This one-way audio channel enable individuals at the television station to send messages to people located away from the station, and is frequently employed during on-location newscasts as the foldback channel to reporters and cameramen. This channel is located at 6.5 times the pilot 102.271 kHz, and is also element of the MTS standard.