Abstract: A processor activates a first monitoring process for initializing a timer and a second monitoring process with higher priority than the first monitoring process. The processor executes the second monitoring process to monitor whether the first monitoring process has been executed. When determining that the first monitoring process has not been executed, the processor executing the second monitoring process determines whether the load state of the processor satisfies prescribed conditions. If the load state satisfies the prescribed conditions, the processor executing the second monitoring process initializes the timer.

Abstract: A transponder among a plurality of transponders that are connected with a client device via a plurality of optical couplers, the transponder includes a protection timer configured to be activated when an alarm indication signal transmitted from the client device is received, and a controller configured to control transmission of an optical signal to one of the plurality of optical couplers when the protection timer times out, wherein a timeout value of the protection timer is set to a value different from a timeout value of a protection timer included in another transponder.

Abstract: A transponder among a plurality of transponders that are connected with a client device via a plurality of optical couplers, the transponder includes a protection timer configured to be activated when an alarm indication signal transmitted from the client device is received, and a controller configured to control transmission of an optical signal to one of the plurality of optical couplers when the protection timer times out, wherein a timeout value of the protection timer is set to a value different from a timeout value of a protection timer included in another transponder.