Modular switching units affecting local network architecture

For versatility stored programme control and multiprocessor arrangements had been introduced to a new line of local exchanges. The decentralization of control is extended to subscriber individual control modules which communicate via a TDM data bus system without additional control. An unidirectional high speed single line data bus can be extended to become part of the local network and subscriber individual control modules are transferred to concentrators in the field which means also reduction of the subscriber loop length. The average prime costs of this two level network can be minimized as a function of concentrator size k. Also power consumption can be minimized as a function of concentrator size k and is affected by the number of repeaters in the unidirectional data bus of the two level network mainly.