Identifying improper cabling of devices

The invention relates to is connected with distributed control system (of transformer substation automation systems) and a communication network control system apparatus for identifying of not correcting cable connection. A (parallel redundancy protocol PRP) claims a standard I, EC62439 comprise transmitting terminal identification or source address and network or associated device interface identification information through a network and sending transmitting and receiving device. Receiving or destination device confirm indicating whether the received information in the special device the interface connected with, and indication the interface device for by correlating, and receiving network plug paging in message identifying. The inside of at least two entirely different transmission device, the invention is not connected communication paths between two diagnosing apparatuses, comprising a generate error cable connection position and/or indication type. The single event preventing preferably is replaced by the error rate; the error rate of calculation, wherein an associated to the received in a network interface device according in a message to a receiving message the probability, and a plug threshold value compares, so for identifying of correcting cable connection.