{HEAD ~ interaction} between {TAIL ~ the cam follower} and the cam curvilinear surface creating a plurality of pushbutton equilibrium states 
between
{ HEAD ~ interaction } between { TAIL ~ the cam follower } and the cam curvilinear surface creating a plurality of pushbutton equilibrium states
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH