Located behind front wall 134 is a controller, 140, which controls the opening and {HEAD ~ closing} of {TAIL ~ the apertures} of matrix 138 
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Located behind front wall 134 is a controller , 140 , which controls the opening and { HEAD ~ closing } of { TAIL ~ the apertures } of matrix 138
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH