When the solenoid is excited, {HEAD ~ the piston} is driven for movement to switch a flow path within {TAIL ~ the housing} 
When the solenoid is excited , { HEAD ~ the piston } is driven for movement to switch a flow path within { TAIL ~ the housing }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL