{HEAD ~ Voltage outputs} 78 and 80 from outputs 68 and 70 are input into a subtracter circuit 84 which provides an output 86 that is the difference between {TAIL ~ voltage outputs} 78 and 80 
{ HEAD ~ Voltage outputs } 78 and 80 from outputs 68 and 70 are input into a subtracter circuit 84 which provides an output 86 that is the difference between { TAIL ~ voltage outputs } 78 and 80
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH