An elevation drive unit supported by the θ drive elevates/lowers an elevation frame under {HEAD ~ the control} of {TAIL ~ an elevation control unit} 
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An elevation drive unit supported by the θ drive elevates / lowers an elevation frame under { HEAD ~ the control } of { TAIL ~ an elevation control unit }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL