I made my thesis at Knorr-Bremse Vasúti Jármű Rendszerek Hungária Ltd. The aim of my thesis is to design a central data processing module. The equipment is the middle part of a three-level system architecture where it creates connection between a measuring and actuator network and a control unit. Parts of my task are the selection of the measure and actuator network bus and the design of its communication protocol besides hardware and software planning of the equipment. The selection of the upper level communication bus isn’t one of the requirements. During the literature review I collected the most important fieldbuses and I selected the communication bus type based on my business consultant’s requirements. I gave additional items to the set of requirements and finalized the specification. After that I created the protocol of the measuring and actuator network and designed the hardware and the software of the module based on the specification. Finally I have made a PC application to test the equipment.