PURPOSE: To integrate an energizing time as long as an element to be maintained is energized even if a software of the element to be maintained is not operated.

CONSTITUTION: While the same power as that of a power source to be supplied to an element 2 to be maintained is supplied and the power is supplied, an energizing time is integrated, and the energizing time of the element 2 is integrated by an energizing time integrating package 3 for outputting its integrated time as a digital signal. The element 2 to be maintained refers to the energizing time of the package 3, and outputs an alarm signal when the referred value exceeds a predetermined value.