Abstract: In X-ray tubes comprising a metal grid, it may occur that the necessary emission current cannot be reached in unfavorable circumstances. This situation is improved by the invention in that the high voltage for the X-ray tube is derived from at least three series connected high voltage generators, the first and the second generator being connected to the anode and the cathode, respectively, of the X-ray tube while the third generator can be connected either to the anode side (in the case of high tube voltages) or to the cathode side (in the case of low tube voltage) by means of a switching device.

Abstract: Filament current values associated with different X-ray tube anode currents and voltages are stored in various locations of a memory. For an X-ray exposure, the measured value of filament current or anode current is compared with the values stored and the values stored are connected, if necessary. Variations of the emission characteristics of the X-ray tubes as caused, for example, by aging are thus automatically corrected.

Abstract: The invention relates to a circuit arrangement useful in an X-ray diagnostic apparatus for supervising the loading of an X-ray tube. A first signal which is dependent on the anode temperature controls an indication and/or a blocking device. A second signal is formed which corresponds to the maximum temperature (T.sub.max) minus a value (.DELTA. T) which is dependent on the exposure load to be expected. The two signals are compared with each other and the indication or blocking device is released if the temperature (T.sub.i) represented by the first signal is lower than the temperature (T.sub.max -.DELTA. T) represented by the second signal.