{TAIL ~ a displacement/drive mechanism} for driving the pickup base in {HEAD ~ a radial direction} of the optical disc; wherein 
{ TAIL ~ a displacement / drive mechanism } for driving the pickup base in { HEAD ~ a radial direction } of the optical disc ; wherein
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH