a light beam scanner within said housing emitting {HEAD ~ a scanning beam} from {TAIL ~ said housing} toward a target field; and 
from
a light beam scanner within said housing emitting { HEAD ~ a scanning beam } from { TAIL ~ said housing } toward a target field ; and
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 OTH