In a plug connector for connecting a field device of automation technology to an energy supply and/or to an evaluation unit, the plug connector includes a connection plug (M12) for the field device, wherein the connection plug (M12) is composed, at least partially, of a transparent material, wherein at least four display elements (gn ye, ye, rd) are arranged in the connection plug (M12). A first display element (gn) signals operational readiness of the field device; second and third display elements (ye, ye) signal two antivalent switch outputs (MIN, MAX) of the field device; and a fourth display element (rd) signals a disturbance or malfunction of field device. A circuit (NOR, XNOR) is provided to detect a disturbance or malfunction of field device based on the antivalent switch outputs (MIN, MAX) of the field device, and to activate fourth display element (rd) upon detection.