http://en.wikipedia.org/wiki/Second_audio_programFor analog TV (PAL and NTSC), various modulation schemes are used in different parts of the world to broadcast more than one sound channel. These are sometimes used to provide two mono sound channels that are in different languages, rather than stereo. Multichannel television sound is used mainly in the Americas. NICAM is widely used in Europe, except in Germany, where Zweikanalton is used. The EIAJ FM/FM subcarrier system is used in Japan.
ееех-спомням си ББС излъчваше звука НА 7.38 от апаратната (може и сега да го прави ) как цепят секундата за шапки;реклами и новини на ойтелсат на 16 и.
Second audio programs are also available in other media. On analog big-dish satellite TV systems, audio programs are manually tuned by their subcarrier frequency, commonly around 6 MHz, often as low as 5.8 or as high as 7.2. These travel the same way as the discrete left and right main audio channels
Though not technically an SAP channel, television stations can also broadcast a "PRO" (professional) audio subcarrier which is used to communicate with station personnel, particularly those engaged in electronic news gathering. This one-way audio channel allows 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 part of the MTS standard.
Stereo TV broadcasting hadn't started in the UK when this Betamax was launched. In those days, it was common for the BBC to broadcast live music concerts in mono on TV and simultaneously in stereo on FM radio. The 'Simulcast' button on the SL-HF100UB enabled the TV picture to be recorded together with the stereo sound from the radio broadcast.