They work from the vaccuum system. There is a dash pot in each wing. They only pull. When one pulls the other one relaxes a bit. The control head controls a vacuum solenoid. Also there is a turn and bank indicator with the system that controls the vacuum flow. For an old system it acutally works quite well as a wing leveller. You can find this system on most older Mooneys and some beechcraft. On some of the mooneys it was on full time and in order for the pilot to turn the yoke he.she would press a button that would release the vacuum to the system. I installed one of these systems out of a Mooney in the first RV-6 that I built. Probably the only RV flying with this type of autopilot.