My Prodigy has three boost settings (B1, B2, B3), plus the normal non-boost setting (B0). There is a boost button to cycle through the settings. The boost settings are programmed to adjust the aggressiveness of the brakes. Higher boost settings apply a higher starting voltage and provide higher voltage for the same rate of deceleration.
I used the thumb wheel to set the MAXIMUM output for the controller. This is independent of the boost. I set it such that the trailer, on gravel, will barely lock up the wheels; it won't lock up on packed gravel or pavement.
I usually leave it on the B1 setting. It provides the best feeling for both highway and city towing. If I'm towing where I need more brakes on the trailer (i.e. wet/slick roads) I set the boost higher. If I need less trailer brakes, I set the boost lower (only done a few times when the trailer brakes felt really aggressive).
Another feature I use on my controller is the reverse function. When stopped with foot on the brake pedal, I press and hold the boost button for 5 seconds until the display shows "r". This disengages the trailer brakes for a couple of minutes so I can back up slowly without the trailer brakes dragging. Especially useful to back up my sloped driveway!
2004 Toyota Tundra SR5 (V8, 4WD, TP, TRD)
2005 Fleetwod Allegance with axle flip
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Me, DW, DS, DD, Dog & Camping Kitty