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