PURPOSE: To reduce down-time by starting a call processing control program immediately for all processors after initial setting is applied to all the processors, taking it system restart when all the processors rise and applying the initial setting of each subscriber and a trunk in parallel with a call processing to a call caused afterward.

CONSTITUTION: A main processor 1 applies initial setting of a memory by the start from a maintenance personal and starts the initial setting to each call processing processor 2 and monitors the reception of the initial setting end processing report from each call processing processor 2. When the initial setting end report is received from all the call processing processors 2, the restart is reported to the maintenance personnel and then the conventional processing is executed. The call processing processor 2 applies the initial setting of the memory by the start from the main processor 1 to apply the initial setting of the hardware. When all the initial setting is finished, the initial setting end report is applied to the master processor 1 and the initial setting of the subscriber and trunk is applied in parallel with the succeeding call processing. Thus, the down-time is reduced.