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