A profibus system consists of one or more masters and one or more slaves, which are connected by bus cables and bus plugs. A bus segment consists of a maximum of 32 field devices.
If more devices are necessary, it is possible to link more bus segments by using repeaters (signal amplifiers). At the end of each bus segment a termination resistor must be used. The number of slaves, which can be operated by a master, is dependent on the internal memory structure of the master. Up to 126 stations can be involved in the maximum configuration of a profibus system. The master is usually realized as a connecting module at the control system or as a pc interface card. Typical slave devices are sensors, actuators, transducers or display elements.