Rexus 80mm Pulse Width Modulated DC Fan

Rexus offers Pulse Width Modulated (PWM) fans that perform at low noise levels by eliminating the power switching noise of the fan. The speed of the fan is controlled by an external PWM signal. The PWM ramps up linearly from a 20% duty cycle up the fan's maximum rated speed. Because the fan can run at lower speeds it is more energy efficient and will therefore have a longer life. The Rexflo fans come in three sizes 80mm, 92mm, and 120mm to suit all your cooling needs.

What is PWM?
Pulse Width Modulation (PWM) refers to the method of applying a signal to the fan that will vary the width of the fan's pulse. An 80% duty cycle means that the fan is "on" 80% of the time and "off" 20% of the time. A 50% duty cycle signal means that the fan is "on" 50% of the time and "off" 50% of the time (similar to a perfect square wave). On a PWM fan, the 4th wire consists of the PWM line and will be directly proportional to the speed of the fan. That is to say, a high duty cycle will produce high speeds and a low duty cycle will produce idle speeds.