The voltage across the sensor capacitor eventually drops below the ¼Vdd threshold causing the comparator 2 output to go to 1 which drives the SR latch Q bar output HIGH. This, once again, begins charging the sensor capacitor. This charging and discharging process repeats as long as there is power to the system. This circuit is now a very good relaxation oscillator. As the capacitance changes in the circuit, the RC time constant changes as well. This varies the frequency of oscillation.