The delayed timebase may start immediately after the main timebase has reached the level at the DELAY potentiometer. But now the following may happen. Assume that the signal to be tested is a pulse train and that the time between two successive pulses is not constant, but varies a little around the set repetition rate. The result will be a somewhat unstable display; this is known as jitter. The time between the first and the second pulses varies a little, as does the time between the second and the third pulses. The third pulse varies twice as much with respect to the first one as the second pulse does. The fourth pulse varies three times as much, and so on.