The Alarm module AM1 is designed to signal system failures. It is to be connected to the VBus® of the controller and issues an optical signal via the red LED if a failure has occurred. The AM1 also has a potential-free relay output, which can e. g. be connected to a building management system (BMS). So that a collective error message can be issued in the case of a system failure. Thus, the reliability and the stable yield of the system are ensured.