a pull down unit which pulls down {HEAD ~ the output terminal} of {TAIL ~ the data transfer unit} in response to an output signal from the second logic unit 
a pull down unit which pulls down { HEAD ~ the output terminal } of { TAIL ~ the data transfer unit } in response to an output signal from the second logic unit
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH