Abstract: The invention relates to a process for the controlling of the position of the focus of an X-ray tube, a applicable to the monitoring of X-ray equipment equipped with X-ray tubes and to the installation of the latter in shields. The invention also relates to a control apparatus for performing the above process. According to the process of the invention, the image of the focus of an X-ray tube is produced on two X-radiation sensitive, contiguous detector means. Each of the detector means supplied an output signal, whose amplitude is a function of the distribution of said image of said detector means. The output signals are applied to a comparison means, which supplies a difference signal linked with the position of the focus along a first given axis.

Abstract: The crankshaft bears a mark which passes in front of a sensor. When the crankshaft is rotated as the engine turns, the sensor delivers a squarewave signal when this mark passes in front of it. The mark and the sensor are positioned with respect to each other such that when the end of the mark passes in front of the sensor the piston is in a given low position and moves up toward the spark plug and such that when the other end of the mark passes in front of the sensor, the piston has substantially reached its maximum stroke within the cylinder in the vicinity of the spark plug, i.e. when it produces the maximum compression of the combustion gases located in the cylinder. The output of the sensor is connected to the input of a reset circuit of a counter and to the input of a count start and stop circuit of this counter and also to the input of a transfer control circuit.