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