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