up fig2 shows an x ray generator 19 and two image receivers 4 5 the image receivers 4 5 each include a sensor 20 for registration of the imaging detector and an exposure measurement device 23 the exposure measurement device 23 is included for controlling the radiation dose when an x ray image is recorded x rays hit the exposure measurement device 23 of the corresponding image receiver 4 5 which measures the x ray dose arriving if the measured x ray dose reaches a predetermined dose limit value a switch off signal is triggered for the x ray generator 19 the switch off signal may cause the x ray source 2 to be switched off the radiation is performed until such time as the exposure of the x ray film cassette has reached the necessary exposure for example slim patients may have a shorter exposure time than corpulent patients the signal output of the sensor 20 for registration of the imaging detector of each image receiver 4 5 is connected in a circuit directly to a signal input for an enabling signal of the x ray generator 19 the x ray generator 19 requests an enabling signal at the signal input an x ray voltage may be created only if the enabling signal is present the sensor 20 does not generate a detector recognition signal for the image receivers 4 5 when an x ray film cassette is not present.