SYSTEM SWITCHING SYSTEM FOR ATM EXCHANGE

PURPOSE:To switch systems without redundantly providing buffer capacity and increasing the number of system communication contact points even in the case of a multistage buffer type ATM speech path. CONSTITUTION:All the buffers of existent and reserve systems 51' are made empty corresponding to a system switching request, afterwards, an input cell a' is multicasted to an existent operating system 51 and the reserve system 51', the same cell flow is applied to both of systems, reading is performed on the same situation in both of systems, and a selector 53 selects the cell from the existent operating system as an output to respective outgoing lines #i (i=1, 2...m). An empty monitor part 52 monitors the empty state of the buffer sharing the outgoing line for each outgoing line xsii of the existent operating system and since the content of buffers in both of systems are coincident after all the buffers sharing the prescribed outgoing line xsii are simultaneously made empty, the system switching part 53 selects/outputs the cell from the reserve system. Afterwards, switching is similarly performed concerning the other outgoing line.