Abstract: The present invention has an additional control device for locally adapting a control signal to be fed to a device-external ventilator having a supply input, a supply output to provide a ventilator supply voltage to the device-external ventilator, a control input, which is configured to receive an actual control signal to be fed to the external ventilator, which actual control signal specifies a desired delivery rate to the ventilator, a control unit with a delivery rate determining unit to capture a power measurement variable correlating with an actual delivery rate of the ventilator, a control signal adapting unit to determine a desired control signal, and a power control unit to output either the received actual control signal or the desired control signal at a control output to the external ventilator in dependence on the result of the comparison.