ATM SWITCH SYSTEM

PURPOSE: To obtain an ATM switch which can consist of only the circuits that can be simply constructed and also can perform the uninterruptible switching operations of the redundant systems. CONSTITUTION: The circuits (T cell detection circuit and staying cell number detection circuit) are provided in a working switch 13 and a stand-by switch 14 to detect the number of cells included in the buffers 21 and 31 when the cells of the prescribed contents are inputted. So that the contents of both buffers 21 and 31 contained in the switches 13 and 14 are synchronized with each other. At the same time, the buffer 31 of the switch 14 is controlled (synchronization of cells of the prescribed contents) in response to the difference of the numbers of detected cells between both detection circuits. Then an ATM switch system has a constitution where the cells are outputted to the outside from the buffer 31 of the switch 14 when the cells of the prescribed contents are detected at the subsequent stages of each switch.