The fourth control theme is thermistor control. A thermistor can be connected to the PWM controller, and a correlation is created between the detected temperature, the duty cycle, and the fan speed. The PWM controller can be set for which it will automatically adjust the fan speed so that the thermistor’s detected temperature matches the controller’s set temperature. The box type controller has an outer scale in Celsius, which allows the knob to adjust the fan speed according to the detected temperature. On the PCB type controller, a switch can be set to allow for the detected temperature.