The PISA backup module monitors not only the individual output currents but also the 24 V power supply voltage for the first time, protecting against voltage drops. A protective shield in the input stage of the PISA module functions like an adjustable valve, allowing only enough current to pass through to ensure that the supply voltage does not drop below 21 V. This enables a safe and uninterrupted supply for sensitive consumers when they are connected to the same power supply as the PISA module. Consumers that are less sensitive to brief voltage drops or that themselves cause faults in the 24 V supply are connected to one of the four current-monitored outputs of the PISA module.