Features include a diode O-ring and dual power feed fusing with a 10-75 Vdc voltage range, jumper-selectable 12, 24, or 48 Vdc operation, multiple sensor inputs, fan current limiting, and a full speed override input. The 1.5 x 5 in. device accepts temperature inputs from up to 3 OR'd sensors and provides proportional speed control to the fans. Maximum fan current is 4 A or 5 A at 55°C for still air and 200 ft/min air stream, respectively. Units also feature soft start and current limiting at startup.