Leeson Electric's DC to DC controllers are a chassis type design, that accept a DC input voltage and output a DC power voltage to control the motor speed. The speed maybe varied with the potentiometer that is shipped loose with the control or an external voltage signal. Higher design efficiency results in longer running time between battery charges than is possible with traditional methods of speed control using resistance in series with the battery. - Leeson Electric Low Voltage Adjustable Speed DC Controller, 12/24V Analog Input, Non-Reversing Rotation.