The duty cycle of the train of {HEAD ~ pulses} produced by {TAIL ~ the controller} 14 and which are fed to the base of electrodes of transistors Q1 and Q2, is determined by the sense voltage produced on line 17 
produced by
The duty cycle of the train of { HEAD ~ pulses } produced by { TAIL ~ the controller } 14 and which are fed to the base of electrodes of transistors Q1 and Q2 , is determined by the sense voltage produced on line 17
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL 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