said output means is further responsive to said third and fourth signal pairs for additionally providing an output signal changer corresponding to {HEAD ~ selected zero crossings} of {TAIL ~ said third and fourth signals} 
of
said output means is further responsive to said third and fourth signal pairs for additionally providing an output signal changer corresponding to { HEAD ~ selected zero crossings } of { TAIL ~ said third and fourth signals }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL