The signal at the collector of {HEAD ~ transistor} 168 is then applied to the base of {TAIL ~ a current drive NPN transistor} 186 via a diode 178 
The signal at the collector of { HEAD ~ transistor } 168 is then applied to the base of { TAIL ~ a current drive NPN transistor } 186 via a diode 178
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH