Abstract: A circuit comprising an oscillator having a load coupled thereto by means of at least one voltage-dependent coupling element that exhibits a high impedance at relatively low voltages and low impedance at relatively higher voltages. The voltage-dependent coupling element can comprise two series connected Zener diodes connected such that the anodes of the diodes are coupled together. The voltage-dependent coupling element can also comprise a varistor.

Abstract: A circuit for controlling the amplitude of video signals includes a control circuit which contains a first capacitor. For each image pulse, a charge which corresponds to the amplitude of the generated video signal during a prior frame cycle is stored in the first capacitor. During the frame flyback pulse, this charge is transferred to a second capacitor by means of a switch. The second capacitor's voltage serves as a control voltage for the video signal. After the charge is transferred to the second capacitor, the first capacitor is discharged.

Abstract: The invention relates to a radiodiagnostic apparatus with an x-ray tube, a diaphragm which is semitransparent at least areawise and which clears a slit variable in its width and letting the radiation go through, with an x-ray image intensifier and a television camera coupled thereto for the generation of video signals which is connected to a monitor for reproduction of the video signals. The diaphragm consists of several individual blades which abut against one another in parallel on both sides of the slit and are adjustable in longitudinal direction individually dependent on the size of the object to be viewed. To the television camera an evaluating circuit is connected which supplies a control signal obtained from the video signal to a setting device for the individual blades.