A clock generator generates {TAIL ~ two kinds} of clock pulses having opposite phases and {HEAD ~ the same frequency} 
A clock generator generates { TAIL ~ two kinds } of clock pulses having opposite phases and { HEAD ~ the same frequency }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD