The output signal from this optical detector 7 is sent via the preamplifier to the RMS DC 18, which converts {HEAD ~ the amplitude} into {TAIL ~ a dc voltage} 
The output signal from this optical detector 7 is sent via the preamplifier to the RMS DC 18 , which converts { HEAD ~ the amplitude } into { TAIL ~ a dc voltage }
OTH 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 REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL