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