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