Orion Fans Reversible Flow DC Fans eliminate the need for two fans and provide excellent cooling performance in both forward and reverse directions. This feature of the fans decreases cost, required footprint, and maintenance and increases product reliability. These DC fans control speed and airflow direction without supplemental excess wire or circuitry, as every model includes Tach/PWM. The reversible flow DC fans maintain airpath consistency and are controlled by the PWM speed control method. This method provides a fixed frequency AC square wave signal to the fan, and the Duty Cycle of the waveform is altered to match the desired speed. Typical applications include vending machines, cooler display cases, outdoor, Heating, Ventilation, Air Conditioning (HVAC), and lighting.