Abstract: The invention relates to a device for the prevention of serious faults in electrical mains supply networks by spectral analysis of the network voltage. The spectrum determined by a voltage A/D converter and a spectral analysis device is subjected to a classification by frequency intervals. The values for the frequency interval classes are correlated in the comparator with frequency interval class reference patterns for corresponding determined faults.

Abstract: A digital measuring device for a quasi-analog measurement value indication includes a display for the measurement value indication, a pre-determined overall measuring range disposed on the display, a measurement value scale forming a spread measuring range section of the overall measuring range with variable spreading, the measuring value scale being addressable in planar segments with alpha numeric characters, an indicating device for indicating a value on the measuring value scale, and an automatic control placing measurement values within the displayed measuring range section with numerically displayed scale values fitting the measuring range section, with the overall measuring range remaining constant and the measuring range section having a selected spreading factor.

Abstract: Digital measuring device, including a trigger generator having an input for receiving an analog measuring input signal, a variable delay line being connected to the trigger generator and having an output, an analog/digital converter receiving the analog measuring input signal, a transient memory connected to the analog/digital converter, a picture refresh memory connected to the transient memory for storing the measuring input signal, a Walsh function generator connected to the picture refresh memory, a liquid-crystal picture screen being connected to and addressed by the Walsh function generator, the output of the variable delay line being connected to the analog/digital converter, the transient memory and the picture refresh memory, and a selectable time base being connected to the variable delay line, the analog/digital converter and the transient memory.