In the thermistor-based "220V Cooling Fan" control, if the ambient temperature rises above room temperature, temperature rise bridge will detect the temperature and turn on the fan. This job is fully automatic, when the ambient temperature returns to room temperature, "220V Cooling Fan" will be closed. Negative temperature coefficient (NTC) thermistor can be very effective in detecting the rise in the ambient temperature. Because it is a negative temperature coefficient, when the ambient temperature rises, the thermistor resistance will be reduced. In this case the temperature of the bridge in the process control "220V Cooling Fan" work, the use of this unique feature is that the thermistor.