The speed of operating structure of an exercise machine is sensed by a sheave and belt drive and rotates a worm gear interconnected to a reduction gear assembly to rotate a driver at a preselected rate. The driver is interconnected to drive a cam surface upon which a cam follower rides to in turn operate...http://www.google.co.uk/patents/US5259611?utm_source=gb-gplus-sharePatent US5259611 - Direct drive controlled program system
