This is accomplished by permitting the disc to be positioned on the shaft driving {HEAD ~ the disc} at a plurality of {TAIL ~ discrete angular positions}, each associated with one of the home position indices 
This is accomplished by permitting the disc to be positioned on the shaft driving { HEAD ~ the disc } at a plurality of { TAIL ~ discrete angular positions } , each associated with one of the home position indices
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH