The extent of {TAIL ~ opening} of the sectors 12a and 12b and the count N of the up down counter 42 have {HEAD ~ a pre established relationship} 
The extent of { TAIL ~ opening } of the sectors 12a and 12b and the count N of the up down counter 42 have { HEAD ~ a pre established relationship }
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD