The improvement 4, wherein each said pressure responsive device includes means for driving said valve therefor toward open position upon {HEAD ~ an increase} in {TAIL ~ the pressure signal} thereto 
in
The improvement 4 , wherein each said pressure responsive device includes means for driving said valve therefor toward open position upon { HEAD ~ an increase } in { TAIL ~ the pressure signal } thereto
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH