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