![STR 5412](https://abouelzahab.com/212-large_default/ic-str-5412.jpg)
When the output voltage decreases, the conduction of the STR starts again repeating the cycle already described. However, not all is said, because the source is working at time intervals that may be different from the one corresponding to the horizontal sweep trace, which may cause some instability – pulsating – in the output voltage.