Method for operating telecommunication exchanges, especially PCM time division telephone exchanges, with distributed switching networks connected to a central switching network

Line trunk groups connected to a central switching network via time-division multiplex lines and exhibiting, among other things, one distributed switching network each and one group processor each are allocated to one another in pairs. Apart from the line units, which are individually allocated to one and the other of two line trunk groups and which are connected via internal lines in normal operation to the distributed switching network of their own line trunk group in each case and which can be switched to the distributed switching network of the other line trunk group in each case, the time-division multiplex lines individually brought to each of the line trunk groups from the central switching network can also be switched from their own line trunk group to the respective partner line trunk group. For further communication of a central processor with the group processors taken out of operation, a channel, used as control channel, of each of the switched-over time-division multiplex lines to the group processor in each case taken out of operation is switched back again by time- division multiplex technology means.