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