{HEAD ~ A first on disc position} is related to an innermost position within {TAIL ~ the second data recorded region} 
{ HEAD ~ A first on disc position } is related to an innermost position within { TAIL ~ the second data recorded region }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL