lm555 timer 78 is resistor 96 here having 500k ohms resistance connected across the dis pin 94 and the thr threshold pin 98 of the lm555 timer 78 is resistor 100 here having 62k ohms resistance the thr pin 98 is connected to the tr trigger pin 102 connected to thr pin 98 is plate 52 of the liquid level sensor 48 plate 50 of the liquid level sensor 48 is connected to gnd the cv control voltage pin 104 of the lm555 timer 78 is tied through or 0 01 f capacitor 106 to ground the reset pin 108 is tied to the vcc line 86 during operation the lm555 timer 78 operates with well known principles and sets the frequency at its output in accordance with the capacitance between thr 98 and gnd accordingly lm555 timer 78 generates a frequency signal onto line 84 which varies proportionately to changes in the liquid level sensor 48 capacitance furthermore the frequency signal will change with the fluid height in tub 12 frequency generation circuitry 42 transmits the frequency signal through line 84 to flow and timer control circuitry 44 it is recognized that the frequency signal varies between gnd and vcc typically 5 v and the noise coupled to the frequency signal is typically around 100 mv hence the frequency signal is substantially immune from noise from.