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