This circuit divides the frequency of an input signal, typically by 2.
Here a 555 timer has an input frequency of 1 kHz. When the input signal at "Trigger" goes low, it triggers the capacitor to begin charging.
The capacitor must then go beyond the 6V Threshold set at the "Control" pin before it responds to the input signal going high, where it will discharge very quickly.
When the Capacitor and Potentiometer are set correctly the timing is half of the input frequency.
T~RC
