The reflectors comprise ruled surfaces and are arranged to converge from {HEAD ~ entrance} to {TAIL ~ exit apertures} 
to
The reflectors comprise ruled surfaces and are arranged to converge from { HEAD ~ entrance } to { TAIL ~ exit apertures }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL