In {HEAD ~ a preferred embodiment}, the frame emulates a workpiece cassette and the distance sensors provide a numerical output of {TAIL ~ the distance} to the workpiece 
In { HEAD ~ a preferred embodiment } , the frame emulates a workpiece cassette and the distance sensors provide a numerical output of { TAIL ~ the distance } to the workpiece
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH