Importance

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Abstract

A digital input is disclosed for supplying a digital signal representing the occurrence of a special event, such as a malfunction, to a recording device. The present invention can be advantageously used in a distribution network for electrical energy, in which the special event triggers the actuation of a switch in a switchgear. The digital input has two first current terminals, to which direct current is applied from an external voltage source. Two second current terminals are connected to a sensor element, for example an auxiliary contact of the switchgear, which outputs the digital signal when the special event occurs. An electrical circuit is also connected to the two second current terminals and carries the digital signal to an optocoupler which provides electrical isolation. The digital input furthermore has a device for converting the direct current supplied from outside the device into a direct current which is electrically isolated therefrom. The device is operatively connected to the two first current terminals on the input side and to the signal circuit on the output side. In contrast to digital inputs according to the prior art, only signal currents are supplied via the two second current terminals. For this reason, only very simple protective measures against electrical and electromagnetic noise levels must be taken at the current terminals.

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First Claim