Four of the optical signals from two of the inspection regions are paired for {TAIL ~ input} into one of the optical cameras and recorded on {HEAD ~ a singular frame} 
Four of the optical signals from two of the inspection regions are paired for { TAIL ~ input } into one of the optical cameras and recorded on { HEAD ~ a singular frame }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD