the pushbutton operable to store {TAIL ~ energy} in and to withdraw energy from the spacer spring while moving {HEAD ~ the contact arm} between first and second equilibrium states 
the pushbutton operable to store { TAIL ~ energy } in and to withdraw energy from the spacer spring while moving { HEAD ~ the contact arm } between first and second equilibrium states
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH