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