A potentiometer is an electric "dial" sort of a thingy - in fact, the reel speed dial in the Series II's is in fact a potentiometer. The potentiometer just replaces the 3-spring control. When part of the cutterbar raises or lowers, it more-or-less "turns" the "dial" on the potentiometer, thus sending an electric signal to the HHC to raise or lower the head. There is a potentiometer on each end of the head and that's how they make the lateral tilt work - if the left end is saying "raise" and the right end saying "lower", the lateral tilt control will tilt the head to the right. To answer your question, if I haven't confused you beyond hope, the potentiometers replace the 3-spring control so they can't be used together. Hope this helps- Tom langan