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