In addition, maintenance workers do not have to adjust {HEAD ~ the projection angle} of {TAIL ~ each visible light beam} each time such an adjustment is required 
In addition , maintenance workers do not have to adjust { HEAD ~ the projection angle } of { TAIL ~ each visible light beam } each time such an adjustment is required
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH