In certain environmental conditions^ objects - as well as human beings - can charge themselves with electrical energy. This can be explained as follows: When two insulating materials with different dielectric constants are rubbed against each other one material transfers electrons to the other. The resulting potential difference is discharged in a short compensating action when another metal object is approacheds whereby an arc occurs and strong magnetic fields are built up. In areas where data processing equipments are installed the relative humidity can drop below 50 % due to the dissipation from the equipment which is given up to the surroundings. Since the danger exists that electrostatic charging takes place with decreasing humidityit is possible that people also charge themselves up in such surroundings. This can take place through friction on a synthetic carpet or between two vestments. The resulting potential can reach several kV. When a conducting object is approached a compensating action occurs, which is felt as a slight shock. The compensating current which flows and the accompanying electromagnetic field leads to malfunctioning or destruction of components in installations which are not sufficiently protected. It is necessary to systematically test such systems which are subject to interference if the economic dis~ advantages cannot be accepted.