The basis of a NET module is a NET-CPU-BASE with Ethernet/USB interface or a NET-CPU-PRO-CS with Ethernet/USB/CAN/serial interface. Up to 64 different NET-DEV-I/O modules can be combined and connected to these NET-CPU base modules. Analog and digital modules can be combined. Depending on the application, digital and analog modules can be mixed. Module combinations with relays, power relays, A/D inputs, and temperature measurement are therefore not an issue. The complete module is mounted on a DIN rail. A service-friendly replacement of a single module is possible. Even during operation, individual modules can be exchanged or replaced. This allows for a service-friendly upgrade or replacement of modules. Upon the next restart of the complete module, the NET-CPU interface first scans all NET-DEV-I/O modules, thereby capturing the overall module configuration.