R116 = 1.2 kΩ · R117 = 1.2 kΩ · coil flyback peak = 300 V · D102 zener = on
Three cycles of a Kettering coil waveform (dwell → 300 V flyback → 50 V burn → ringing → 13 V open). Move the pointer over any panel to read all three signals at one time instant.