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