The two pairs of {HEAD ~ signals} are signal processed to enhance {TAIL ~ resolution} of the ring laser readout 
The two pairs of { HEAD ~ signals } are signal processed to enhance { TAIL ~ resolution } of the ring laser readout
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH