The ATS must work the same way it did in the 8 mm. video decks. In them, there are four rotating frequencies used. The primary on track frequency is the strongest coming out of the head, two other frequencies are expected at lower levels. The capstan motor is adjusted by the servo to equalize the two off track frequencies.
At each pass of the head it uses a different frequecy for the on track frequency and of course it expects two other frequencies just the same as last time.
There are four frequencies and the reason for that rather than just three is to keep it from getting confused. When F1 is recieved it KNOWS it is looking for F2 and F4 for example, then when F2 is on track it looks for F1 andF3, then when it goes to F3 it looks for ........ I forget. It doesn't matter, but this should illustrate the reason to use four frequencies rather than only three. It assures the proper operation of the servo because there can be no mistake about which track is leading the "on" track and which is lagging.
This system eliminates the need for a control head and errors introduced due to tape stretching. The 8 mm. decks did actually usually have a sub audiohead but I doubt it was ever used except maybe in some super cheapo deck which didn't even make it to market. It may have been used for a tape counter as well, I simply don't remember those details.
Interestingly there were decks that used the 8 mm. tape strictly for audio.The tape wrap was actually greater than 180 degrees and one sector was used for digital audio tracks. These were not the greatest format in the worldbut they beat BTSC and were good enough for music, as in better than most cassettes. The 8 mm. decks with the feature to go all audio simply used more sectors for more digital all audio mode. If you recorded say tracks 5 and6 on a tape that had video on it you would see a band across the screen where the new audio tracks were recorded. The system also had the drawback ofhaving to completely rewind before playing the subsequent tracks.
Needless to say these things did not get a huge market share. I just know about them because I worked for a high end Sony dealer.
This is completely different than the auto tracking feature in any VHS deckand I am unaware of automatic tracking being incorporated in any Beta deck, though I might not have seen them all.
Additionally, in the DAT formet I don't know, and I simply don't remember on the 8 mm. decks if the actually recording carrier frequency was rotated or if they were like "pilot" frequencies simply chosen not to interfere withthe signal, but it really doesn't matter. That's how such a system works.
