A force motor is operable when desired to move the slide valve to its open position to permit {HEAD ~ movement} of {TAIL ~ the member} 
of
A force motor is operable when desired to move the slide valve to its open position to permit { HEAD ~ movement } of { TAIL ~ the member }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL