In the device a controllable switch is built into the control device which enables the start authorization and by means of which the supply voltage with which this controllable switch is supplied can be switched off. To check a start authorization a diagnosis can be undertaken which is realized with known resistance elements in the voltage supply line between identification device holder and control device. This allows the voltage drops across the elements to be compared with the corresponding required values. Simple short circuiting of the starter or the ignition is thus no longer possible since this would be detected by the control device as a result of the changes in voltage drop. In addition a fault in the supply voltage or the feed lines can be definitively detected.