A device and a process are provided for recognizing a correct use of an alcohol measuring device by a test subject. At least one alcohol measuring device is provided with a signal transmitter, an analysis and control unit and a camera unit. An image field of the camera unit is divided into an inner image field area and an outer image field area. The inner image field area detects at least the face area of the test subject. The camera unit records changes at a boundary between the inner image field area and the outer image field area. A signal sent by the signal transmitter in the inner image field area can be detected by the camera unit.
