The box type PWM controller is a convenient item to have as a laboratory tool. Instead of having to use a function or pulse generator, which are usually found in small numbers in a lab, the PWM controller is a cost-effective way to test out fan performance. It is compact in size, easily connects to fans, and the PWM duty cycle can be adjusted with a dial knob. The Box type controller allows for 4 control themes; dial, voltage, external adjustment, and thermistor control.