A centralized supervisory control system allowing a centralized supervisory control center exactly to grasp information about failures and other events occurring in a plurality of supervised apparatuses, the center being also notified of time-of-day indications corresponding to such occurrences. Each of the supervised apparatus turns its information into blocks for output to an intermediate control apparatus. The intermediate control apparatus continuously collects such status data from the supervised apparatuses and compares the data with the status data currently held in its memory. If the latest status data from a given supervised apparatus are found to contain a deviation from the old data, the latest data are stored in memory along with a time-of- day indication corresponding to the deviation. The latest status data and the time-of- day indication are sent to the centralized supervisory control center. The intermediate control apparatus transfers chronologically the information from the multiple supervised apparatuses to the centralized supervisory control center. If the centralized supervisory control center is stopped or if line disconnection occurs, the previously collected information about the supervised apparatuses is controlled chronologically by the intermediate control apparatus. When the centralized supervisory control center resumes its service, the information about the supervised apparatuses is transferred to the centralized supervisory control center. If the memory area for accommodating supervised apparatus information becomes full, the oldest information is deleted therefrom on a first-in first-out basis to make way for the new. The status data in the same block as that of the deleted data are then transferred to the centralized supervisory control center.
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