To carry out these operations, {HEAD ~ the optical head} 13 is moved radially over {TAIL ~ the optical disk} 11, so that a laser beam spot is positioned at a predetermined track 
is moved radially over
To carry out these operations , { HEAD ~ the optical head } 13 is moved radially over { TAIL ~ the optical disk } 11 , so that a laser beam spot is positioned at a predetermined track
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH