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