Abstract: In X-ray examining apparatus in which a compression counterweight is uncoupled in the vertical position, a problem exists in that, when the examining apparatus is turned over, the compression counterweight is coupled to the X-ray image section with a jolt. So as to avoid this jolt, pneumatic damping devices are known which, however, are very voluminous. According to the invention, a simple and efficient device for the damped coupling comprises a control circuit which brakes the counterweight when it exceeds a given speed.

Abstract: The servo drive according to the invention includes a force transducer which is disposed so as to sense all the forces which act on the image-forming section (the weight of the section, the manual force of the user, frictional forces and acceleration forces). On the signal from the transducer there is superposed a signal which corresponds to the weight of said section and to the speed variations dn/dt, i.e., to the acceleration forces. Thus the influence of these forces on the output signal is compensated for. The resulting signal serves as the desired value for a speed or acceleration control.

Abstract: X-ray examining apparatus generally conprise various supervisory circuits which must prevent, for example, that the table top is lowered too far when the table is in the vertical position or that the pressure exerted on the patient becomes too high. The quantities to be supervised are simulated by the voltage to be derived from the potentiometer, and if such a potentiometer becomes defective it may occur that the supervisory device is not actuated. It is also possible that the supervisory circuit itself is defective. In order to detect such a defect, a fault-simulation generator is provided which during operation is connected at regular instants to the input of the supervisory circuit instead of to the potentiometer tapping and which generates voltages which correspond to a failure. If the supervisory circuit is not actuated in such a case, it means that it is defective. This defect can be signalled by the test circuit.