A control device with an electric servo motor is proposed, by means of which a throttle device can be operated, which opens, to a greater or lesser degree, the passage diameter of a flow line, especially the passage diameter of a by-pass line around a throttle valve disposed in the intake line of an internal combustion engine. The control device has an elastic element which moves the throttle device, during an interruption of the current supply to the electric servo motor into a defined position opening the passage diameter of the flow line.