Abstract: In a control device, especially for heating and ventilation systems in mo vehicles, comprising a rotatable control knob and a linearly movable setting member, a lever is provided for coupling the knob and member and converting rotational motion of the knob into linear movement of the setting member. To achieve this, the control knob 2 is provided with a guide slope extending at an acute angle to the axis of rotation. A shorter arm portion of the lever is controlled by the guide slope. A longer arm portion of the lever is actuated by movement of the shorter arm portion against the guide slope and acts upon a coupled setting member in a linear manner.