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