Another bit of information I got from the TT rep at the Lardy seminar this summer is that the frequency changes between between low, medium and high when the switch is on continuous. The signal amplitude (voltage output) is set with the dial and the signal frequency increases from low to medium to high with the two buttons.
Another interesting thing he had was the "truth box". It displays when the handler corrects the dog and the setting used on the collar. This is useful for determining if the handler really corrected the dog when they say they did, and vice versa. Mike was able to watch what the handlers were doing to the dogs and not depend on what the handlers said they did. ; - )