When the parameter to be sensed reaches a predetermined value or configuration, {HEAD ~ the switching apparatus} may, by means of electronic signals, cause {TAIL ~ the first valve apparatus} to close 
cause
When the parameter to be sensed reaches a predetermined value or configuration , { HEAD ~ the switching apparatus } may , by means of electronic signals , cause { TAIL ~ the first valve apparatus } to close
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH