{HEAD ~ a spool} provided in {TAIL ~ the casing} and configured to switch the output port between the pump port and the tank port, and 
provided in
{ HEAD ~ a spool } provided in { TAIL ~ the casing } and configured to switch the output port between the pump port and the tank port , and
HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH