The level-translator (P14 and P3) is like a comparator. When the level is above the threshold, the output-of the level-translator is “1” (high) and when the level is below the threshold, the output of the level-translator is “0” (low). Using the potentiometer allows the engineer to move the sawtooth-waveform up and down and the more it is moved up, the wider the pulse of the output becomes, resulting in a wider pulse-width in the PWM. When shifted down, only the peak of the saw-tooth is above the threshold, resulting in a very small/narrow pulse. We are showing this behavior using an ADC (P13) sampling the output of the level-translator.