The needle valve dispenses fluid when the activator acts on {HEAD ~ a piston}, which shifts {TAIL ~ the spool} or needle into the open position 
The needle valve dispenses fluid when the activator acts on { HEAD ~ a piston } , which shifts { TAIL ~ the spool } or needle into the open position
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH