PURPOSE:To prevent the omission of input control information during the switching of asynchronous PRE, by performing the in-use/stand-by switching of a device to be controlled by a set-mode switching and discriminating method after predetermined time. CONSTITUTION:Switching controller CTL has two kinds of mode (1 and 2), which are stored in mode display part 18. In normal operation, PRE of the system designated by ACT display part 17 is determined by selection part 16 and read control part 9 extracts and sends only change information on the ACT side to switching control part 14. For the system switching of PRE, the name of the device which was the SBY system in display part 17 and display part 18, when the device is placed is placed in mode 2, receives the end signal from timing control part 19 after the prede termined time passes and resets display part 18 in mode 1. In mode 2, selection part 16 determines the opening and closing of switches A and B, which are driven by switching control part 15. Therefore, control part 9 extracts the change information on PRE of both the systems in mode 2 and then actuates control part 14. Consequently, the input control information is never omitted during the system switching.