Coupling device for a data transmission network and data communications network

The present invention relates to a coupling device for connecting each of two servers (6a, 6b) having a data transmission network (1) and a data transmission network (1) with such a coupling device (3). This has a first and a second terminal (5a, 5b) for connecting a first and a second server (6a, 6b) and a third port (4) for connection to the data transmission network (1). Further, it has a switch device (7) having a first switching state in which the third connection (4) to the first terminal (5a) and from the second port (5b) is separated, and a second switching state, in which the third connection (4) to the second terminal (5b) and from the first terminal (5a) is separated. Finally, it has a with the switch device (7) electrically connected to power supply means (8; 14, 15) for supply of the switch device (7) with energy, with either said first server (6a) or the second server (6b) is connected to or can be connected and is adapted to then by the relevant server (6a, 6b) to apply energy and to provide a power signal to the switch device (7). The switch device (7) is adapted to assume one of the first and the second switching state when the Energievorsorgungseinrichtung (8; 14, 15) is supplied with the power signal, and the other of the first and the second switching state to take when it from the power supply means (8; 14, 15) is not supplied with the energy signal.