Abstract: A hierarchical network management system is described which includes concentrators (2A to 5A) on the individual levels (E1 to E3) of the hierarchy as well as adjustable interfaces in the concentrators for point-to-point and bus connections. An interface is provided for a bus connection on a master side. The interface takes delays into consideration. A transmission channel can be connected to the interface. The channel includes a forward bus and return line (a5, b5). Parallel addressable apparatus (8A, 8B, 8C) can be connected to the forward and return lines. A controllable change-over switch (A8, B8, C8), inserted in the return line (b5) of the transmission channel, is provided for each addressable apparatus (8A, 8B, 8C) of the parallel combination.

Abstract: A communication element for a hierarchical management network enhances the reliability of such a network. The communication element features at least 2 interfaces (2, 3) each having an assigned port (7, 8). A connection to communication elements of a higher hierarchical level of the management network can be established via each interface. A further variant of such a communication element features by at least two interfaces (4, 5) to which is assigned a shared port (11) and via each of which a connection to communication elements of a lower hierarchical level can be established. A further variant of a communication element includes features which can be formed from a combination of all the features of the two first variants. Structures of management networks are made possible with the communication elements presented, are explained.