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