Toimintavarma kolmen tietokoneen monitietokonejärjestelmä

To each computer (MCA, MCB, MCC) are allocated two hardware comparators (VAR, VAL; VBR, VBL; VCR, VCL) to compare the data from itself with the corresponding data from the partner computers. Only if both comparators (VAR, VAL) allocated to a computer (MCA) detect differences between the data fed to it (DA and DB or DC) is the computer shut down via an AND element (UA). The comparison processes are initialised not only by the computer (MCA) allocated to the comparators (VAR, VAL) but also by a partner computer (MCB or MCC). It is thus made certain that in the event of a breakdown the comparison processes for recognising and shutting down a defective computer actually take place and are not sabotaged by the defective computer. The result of the shutdown (ASSA) of a computer (e.g. MCA) is controlled by the operative computers (MCB, MCC), triggered by the interrupt from an allocated error store (FAL, FAR). If the defective computer is not shut down, the operative computers cause the shutdown themselves (total shutdown). The safe multi-computer system is especially intended for use in railway signal systems.