a selector element having a first input, {TAIL ~ a second input}, an output, and {HEAD ~ a control signal}, wherein: 
a selector element having a first input , { TAIL ~ a second input } , an output , and { HEAD ~ a control signal } , wherein :
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH