Abstract: A system for supplying a selected voltage between the anode and cathode of an x-ray tube independent of power source voltage variations couples the x-ray tube power supply to the source with a transformer whose output voltages are selectable with tap switches. Prevailing source voltage and selected applied voltage are sensed and represented by analog signals which are converted to binary digital codes that form addresses for a read-only memory. The read-only memory is programmed with data representative of the pattern in which the tap switches should be set for the transformer to supply the selected voltage at the prevailing source voltage. When addressed by combinations of code words representative of the selected and source voltages, the memory outputs a code word that is used to set the switches in the corresponding pattern.

Abstract: An adjustable focus x-ray tube has its cathode connected to the negative side of a dc power supply which is below ground by half of the total voltage applied to the tube and its anode connected to the positive side of the supply which is above ground by half of the applied voltage. A voltage divider is connected between the negative side or cathode and ground and an intermediate point on the divider is connected to a focusing electrode in the x-ray tube for providing a focusing bias voltage. Since the bias voltage is derived from the cathode-to-ground voltage it will always track or remain proportional to the cathode voltage so the effect of variations in the latter on focusing will be negated.