Does anyone know specifically how a compound bow achieves the pull letoff? I don't have one to look at and I can't figure it out from pictures. It looks like the cams change the length of the limbs as the string is drawn but it doesn't seem like enough to get a major decrease in the pull at full draw. It also looks like there is some pulley action. An amazing invention however it works (never mind that it helped to ruin archery back in the day).