That's a Grandee. Same size as the Vista- 8'4" by 7'7" - and both are about 500 gallons.
The "A" handles are diverters. They send the water pressure to the JetStream jets - like fire hoses underwater - or to certain regular jets. They give you flexibility: you can run two out of the three jets in two of the seats, as you want, you can run the huge jets only when you want to use them, and you also get a spa that does a great job with smaller pumps, for a big energy savings. On the Grandee, the diverters are two-way, and you can leave them in the middle position to have every single jet in the tub running - at a bit less pressure. BTW, that's exactly how I used to do my Grandee, and I have heard many of our customers say the same - even in the mid-position, the jet action is great.
The "B" handles are all air controls. They control the amount of air that comes out of the jets nearby. Some of them are for seats with a Moto Massage - the moving jet - while others do groups of the small "Precision" jets - such as the quartet of P jets over each Moto, or the wall of P jets in the corner seat.
The combination gives you great adjust-ability - I have had a Grandee for many years, and I may switch back to the Grandee from my Vista at the end of this year...
Ironically, I am sitting at my desk looking out the window at a 1989 Grandee sitting on the trailer in front of my house. I sold it to the youth pastor at our church, and today I get to go figure out how we are going to get it into their yard....
