means for supplying {HEAD ~ two kinds} of clock signals having the same frequency and {TAIL ~ a phase difference} of 180 degrees; and 
means for supplying { HEAD ~ two kinds } of clock signals having the same frequency and { TAIL ~ a phase difference } of 180 degrees ; and
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH