{TAIL ~ the second valve} is operable only between a valve open position and {HEAD ~ a valve closed position} 
{ TAIL ~ the second valve } is operable only between a valve open position and { HEAD ~ a valve closed position }
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD