For each digital input signal, {HEAD ~ a pair} of references is selected according to {TAIL ~ the state} that represents the input signal 
is selected according to
For each digital input signal , { HEAD ~ a pair } of references is selected according to { TAIL ~ the state } that represents the input signal
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH