bar 62 diode 86 allows a fast discharge for the falling edge of this signal as potentiometer 88 is varied the dc reference voltage applied to pin 6 of differential comparator 76 will vary and in turn will produce a variable phase difference between the shaped input signal applied to pin 5 of differential comparator 76 and the square wave output signal at pin 7 of differential comparator 76 likewise as the capacitance on touch bar 62 is changed the phase difference between the shaped input signal of pin 3 on differential comparator 90 and the square wave output signal at pin 1 of differential comparator 90 will change in summary in one case first differential comparator 76 has a fixed shaped rising input with a variable dc reference and in the other case second differential comparator 90 has a fixed dc reference determined by resistors 92 and 94 with a variable shaped rising input due to the changing capacitance of touch bar 62 in both cases there exists a potential variable phase change between the input signal and output signal of the comparators referring to flip flop device 96 the state of the flip flop included in this circuit depends on a relative timing of the clock pulse applied to its pin 3 via differential comparator 76 and the variable input.