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