The Profibus I/O systems of the PROFI-8000 series consist of a basic housing with 1, 2, 4 or 8 slots for plug-in modules, depending on the model. The ModbusTCP protocol is used for communication. The slots can be used for I/O modules in plug-in design that comprise both multi-channel analog input/output modules and digital input/output modules. The I/O systems act as slaves in the Profibus network.