The positions of the tracers is determined by {HEAD ~ differential transformers} having {TAIL ~ cores} fixed for radial movement with respective tracers 
having
The positions of the tracers is determined by { HEAD ~ differential transformers } having { TAIL ~ cores } fixed for radial movement with respective tracers
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH