generating and outputting {TAIL ~ a robust phase error signal} representative of {HEAD ~ said robust phase error}; and 
generating and outputting { TAIL ~ a robust phase error signal } representative of { HEAD ~ said robust phase error } ; and
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH