1PWM Speed Controller: This PWM fan speed controller adopts PWM control technology to realize temperature control and speed regulation. The fan speed can be controlled according to the tested temperature. The higher the temperature, the faster the speed, the lower the temperature, the slower the speed 2Auto Stop: This PC fan speed controller controls the fan to stop running when the ambient temperature is lower than the set starting temperature. 3Adjustable Mode: This PWM fan temperature controller supports start up temperature adjustment(10 to 50), turn the switch to the A position and to switch to the adjustable mode. 4Fixed Mode: Flip the switch of this PC fan speed governor to the F position to switch to the fixed temperature mode(30), which won't be affected by potentiometer. 519.7in Cable: This PWM fan speed governor is designed with approximately 50cm/19.7in cable which can be easily connected to your computer chassis.