Abstract: In a circuit configuration for clock-controlled time division multiplex telecommunications switching installations, including PCM telephone switching installations with central switching network and connected subswitching networks, line groups are connected to a central switching network via time division multiplex lines and have one subswitching network and one group control unit each are pairwise assigned to each other. Line units which are individually assigned to the one or the other of two line groups are, in normal operation, connected to the subswitching network of their own line group and can be changed over to the subswitching network of the particular other line group in standby operation. In the line units, equalizing memorys are provided in duplicate and, specifically, in each instance for the message stream to and from line group-common subswitching network, on the one hand, and for the message stream to and from the subswitching network of the particular partner line group.

Abstract: In a circuit arrangement for telecommunications exchanges, including PCM time division multiplex telephone exchanges with a central switching array and connected subordinate switching arrays, line terminal groups connected to a central switching network by way of link connections where each line terminal group has its own subordinate switching array and a group control unit are arranged in pairs. Within each line terminal group, there is terminal equipment for connection of outside lines on the one hand, and on the other hand link terminating circuits for the link connections to the central switching array can also be switched from the subordinate switching array of the respective line terminal group to that of the partner line terminal group. Terminal equipment and link terminating circuits as well a subordinate control units with subordinate switching arrays are equipped with three internal power supply systems and three internal clock pulse supply systems per line terminal group.

Abstract: A circuit arrangement for telecommunication switching systems, including PCM time division multiplex telephone switching systems, with double central switching matrix by which two corresponding line trunk groups comprising a sub-switching matrix each and a group control unit each, are allocated to each other in pairs via two time-division-multiplex lines. The line units and the PCM-lines leading to the central switching matrix, which are individually respectively allocated to the two line trunk groups, and which are connected with the respective sub-switching matrix of their own line trunk group during normal service, are switchable, during emergency service of one of the two line trunk groups, to the sub-switching matrix of the respective other line trunk group.