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