when {HEAD ~ the third number} of shock events falls below {TAIL ~ a lower event threshold}, decrease the shock threshold to the initial shock threshold 
falls below
when { HEAD ~ the third number } of shock events falls below { TAIL ~ a lower event threshold } , decrease the shock threshold to the initial shock threshold
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH