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