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