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