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