 generating {HEAD ~ a negative transition} in response to the signal selected in {TAIL ~ sub step B} 3 
generating { HEAD ~ a negative transition } in response to the signal selected in { TAIL ~ sub step B } 3
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH