A communication module for connecting electrical host devices, each with an individual physical interface, to different external networks, where the communication module is connected to the host device via an interface and provides at least two physical interfaces, and where the communication module has a network connector which is adapted to the respective external network. In order to enable development of communication modules independently of the individual host device and to reuse them for many different host devices, provision is made for the host device to have a processor for identifying the communication module and for selecting the at least one physical interface which is suitable for the host device by means of serial communication.