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