A microprocessor-controlled standard field device, such as a measuring sensor or an actuator, is connected to a field bus system that, in turn, is connected to, for example, a freely programmable controller. The field device is equipped with a security layer for carrying out a security proven communication. A secure and simultaneously cost-effective communication with a control device via a field bus system is made possible by implementing a security layer in, e.g., a conventional operationally proven or redundant standard field device.