In response to positive going pulses fed to the base of transistor Q1, such transistor Q1 is driven from {HEAD ~ a non conducting condition} to {TAIL ~ a conducting condition}, as shown in FIG 4A. Similarly, a train of positive going pulses is fed to the base of transistor Q2 by controller 14 via line 13, as shown in FIG 4B 
In response to positive going pulses fed to the base of transistor Q1 , such transistor Q1 is driven from { HEAD ~ a non conducting condition } to { TAIL ~ a conducting condition } , as shown in FIG 4A. Similarly , a train of positive going pulses is fed to the base of transistor Q2 by controller 14 via line 13 , as shown in FIG 4B
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH