Two operational amplifiers 68 and 70 form part of circuit 50 with inverting terminal 72 of {HEAD ~ op amp} 68 common with {TAIL ~ anode} 54 of photodiode 52 
Two operational amplifiers 68 and 70 form part of circuit 50 with inverting terminal 72 of { HEAD ~ op amp } 68 common with { TAIL ~ anode } 54 of photodiode 52
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH