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