When {HEAD ~ ball} 345 is forced up by {TAIL ~ gas pressure}, the current flowing between electrode 340 and electrode 342 is interrupted 
is forced up by
When { HEAD ~ ball } 345 is forced up by { TAIL ~ gas pressure } , the current flowing between electrode 340 and electrode 342 is interrupted
OTH HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH