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