A field device of a room automation system or of a power management system or of a hazard detection system is disclosed. The field device includes at least one human-machine interface with at least one memory configured to store physical layer data, at least two protocol stacks, wherein the field device is configured to select at least one protocol stack based on the physical layer data stored in the memory of the human-machine interface. The field device also includes at least two physical layers, at least two pairs, wherein each compatible pair includes at least one physical layer and at least one protocol stack. The field device also includes selector switch(es) configured to connect and to disconnect physical layers and protocol stacks, such that a physical layer element and a protocol stack connected or disconnected by the selector switch(es) belong to the same compatible pair.
