Beyond control, regulation, and visualisation, communication is playing a ever-more-decisive role in today’s automation technology. Closely related is the effort given to continuously improving efficiency and flexibility. The primary concern is the exchange of information between system components. Signals from sensors and actuators, for instance, must be channelled to a superordinate automation device or vice versa. The digital data processing performed in such device makes it a great advantage to perform the transmission of these signal digitally. This is where the bus systems come in the form of two-wire connection to which each individual component is connected. Their most important characteristic is their real-time capability and immunity to interference. At the field level, in the process-oriented part of the system, so-called fieldbus systems with master-slave communication are used.