This waveform was captured by setting the trigger at a point between the top of the highest pulses and the top of the lower pulses.

Setting the trigger to this position will stabilize the signal. Setting the trigger to a voltage level below the top of the shorter pulses will result in a clutter live display.

Once the trigger is set you can adjust the time per division setting to take a close look at the pulses. Note that the pulses are arranged in two obvious groups - short and tall.

A 200uS time per division setting allows for detailed examination of the pulses. Note the pulse width variations.