The first counter is reset when the value of {HEAD ~ the second counter} reaches {TAIL ~ a prescribed value} 
The first counter is reset when the value of { HEAD ~ the second counter } reaches { TAIL ~ a prescribed value }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL