Initially transistor Q1 is triggered, through the collector near the ground potential; resulting in about 300 V between the collector and emitter voltage across the second transistor Q2. This second transistor, Q2 experiences a nondestructive avalanche breakdown due to this over voltage. Consequently each transistor in turn experienced an even greater overvoltage due to a faster rise time and a shorter delay. Finally, transistor Q16 is turn to experience the high voltages, fast fall time.