The sensor includes a light source and {HEAD ~ a receiver} which is sensitive to {TAIL ~ its radiation} 
is sensitive to
The sensor includes a light source and { HEAD ~ a receiver } which is sensitive to { TAIL ~ its radiation }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL