Abstract: A damper unit for an air circulation system. The damper unit includes a frame defining an air flow opening, a damper vane for opening and closing the air flow opening, and a drive mechanism for turning the damper vane between the open and closed positions. The vane of the damper unit includes a main body and vane turning surfaces that project outwardly from the main body. The vane turning surfaces are configured for converting air flow into torque for assisting the drive mechanism in turning the damper vane between the open and closed positions.

Abstract: A damper unit for an air circulation system. The damper unit includes an air flow opening, a damper vane for opening and closing the air flow opening, and a motor for moving the damper vane between the open and closed positions. The damper also includes at least two ports, each port being operable in an input and an output mode. When a control signal is received on one port, the signal is sent out on the other port, and vice versa. The ports can be identical in shape to receive the same shaped plug.