Orion fans offer a variety of special functions for its DC fans. These special functions provide end users with intelligent control options and feedback that optimize fan performance and maximize energy conservation. The Tachometer output provides design engineers with an accurate means of monitoring and reporting a fan’s rotational speed, as well as triggering of an alarm or indicator if the fan’s speed falls below a certain RPM, both of which help to maintain consistent optimal fan performance. The PWM input varies the width of the electrical pulse in order to control the average voltage delivered to the fan, allowing for a higher efficiency than linear control provides.  The PWM option also allows users to digitally control the speed of the fan by varying the electric pulse running to it. Thermal speed control employs a thermistor-controlled circuit that increases fan speed only when the temperature rises above a determined set-point, thus reducing overall energy consumption by lowering fan speed when temperatures within the enclosure are below the set-point. The constant speed function senses variable input voltage, which causes variations in power output, and maintains the fan’s constant speed regardless of input voltage fluctuations.