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