The ATX P4 power supply has fan speed control switch which offers 3 selections
as auto, medium or low. When fan speed control is set to auto, it will
control fan speed automatically according to computer system temperature; set to
low for low speed; set to medium for medium speed. Also the patented Thermal
Fan Controller inside the power supply can control up to 3 power supply fans
at the same time to reduce the fan noise as silent as possible. And the thermal
sensor will detect if any fan fails thus prolong the power supply life.