Abstract: A back-up control system of a redundancy configuration suited to be used for a time division switching network. The control system includes connecting paths extending from each of the load supply devices, the paths being classified into an active connecting path and a corresponding standby connecting path coupled to different ones of the load accommodating devices which are provided in a number equal to or larger than three. The total load accommodating capacity of the load accommodating devices is provided with a margin or excess capacity which is smaller than the capacity required for accommodating all full loads supplied from the load supply devices but is not smaller than the load accommodating capacity of any one of the load accommodating devices. At least one of the load accommodating devices is connected to the active connecting path and the spare connecting path which corresponds to another one than the just mentioned active connecting path.