The invention 7, wherein the first detent means comprises an annular array of detent teeth, a first segment of {TAIL ~ the array} comprising a first number of detent positions and a second segment of {HEAD ~ the array} comprising a second number of detent positions; and 
The invention 7 , wherein the first detent means comprises an annular array of detent teeth , a first segment of { TAIL ~ the array } comprising a first number of detent positions and a second segment of { HEAD ~ the array } comprising a second number of detent positions ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH