The principles of the present invention are particularly useful in an optical arrangement generally indicated at 20 for use with {HEAD ~ a passive infrared motion detector} for monitoring {TAIL ~ a space} 
The principles of the present invention are particularly useful in an optical arrangement generally indicated at 20 for use with { HEAD ~ a passive infrared motion detector } for monitoring { TAIL ~ a space }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL