The thermistor decreases the current resistance as it gets hotter. The printed circuit board sends a current to the thermistor and can tell whether less or more heat is needed by the resistance in the thermistor.
Fits a Number of Appliances
Technical specification
Waist Sizead65cd38fwTypeThermistorToilet Cistern CapacityFTW--Supplier Part NumberC08208000Brand NameKeston