PURPOSE: To switch a main console to a substitutive console automatically by outputting a machine check report to the substitutive console and opening a private interface when a fault is generated in the main console.

CONSTITUTION: When any one of a machine check signal group 19 on the main console A side is turned on, a machine check interruption setting signal 20 sets an FF and the signal 20 is transmitted to the console B side (substitutive side) through a machine check interruption signal bus 23. When receiving the interruption, a console processor generates a set inabling signal 24 to switch a console interface so that said processor itself acts as a main console. Consequently, a selecting signal inable A on the main console is suppressed, a data I/O bus in an interface bus is suppressed and the console processor itself is separated from a system so that the other console can use the bus.