angular position determining means connected to said {HEAD ~ engaging means} for {TAIL ~ rotation therewith} and for providing an indication of the angular position of said engaging means; and 
for
angular position determining means connected to said { HEAD ~ engaging means } for { TAIL ~ rotation therewith } and for providing an indication of the angular position of said engaging means ; and
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH