In order to monitor the number of plug cycles of a plug, such as a plug of a charging cable for an electric car, a plug cycle counter associated with the plug is counted up in an electronic memory after every plug cycle. A warning can thus be issued when a permitted quantity of plug cycles for the plug has been exceeded. Alternatively, the electrical connection at a charging station for an electric car or at a data cable for an automation system can also be cut off if the service life of the plug has been exceeded. High availability of the plug is thereby achieved, because the corresponding cable can be replaced in a timely manner. A hazard to persons due to defective current-carrying parts is also prevented.