Abstract: A multiprocessor alarm data processing system includes a database with identifying information for all the central stations and their subscribers who use the system. Several input processors receive alarm data from the central stations to identify subscribers incurring alarm events. The input processors generate event records for alarm data validated against the database. Several output processors are provided to process the event records to select the appropriate municipal authority and transmit thereto identifying information for a sucscriber incurring an alarm event. The processors may be switched between input and output processing for dynamic internal load shifting and redundant processing systems are provided for inter-system load sharing. A busy-out capable modem is provided to facilitate such inter-system load sharing.