The first input signal is applied to a base or {HEAD ~ gate} of {TAIL ~ the second transistor} with regard to said reference point 
The first input signal is applied to a base or { HEAD ~ gate } of { TAIL ~ the second transistor } with regard to said reference point
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH