In order to detect the current state of a system component, e.g. to display whether an electrical conductor, a cable or the like, is currently live, a field generator that generates a magnetic field in the environment of the system part is provided, which generator is connected to an organic magnetoresistive OMR semiconductor element that is arranged stationary in the environment of the system component to be monitored, and a voltage source for generating an electrical voltage between two electrodes of the OMR semiconductor element is provided. The device and the method can be fitted in a simple manner and cost-effectively to almost any system part, even at a later stage to already existing systems. A corresponding display shows the desired information locally limited and in the simplest manner: if the electric conductor is currently energized, an additional evaluation is not necessary.