To display the state of a fault, etc., on the screen of a computer device, etc., when a protecting function operates owing to abnormality, etc., of a power circuit or load circuit to turn off the power source.

A power source part 3 transforms and rectifies the voltage of a commercial power source 1 to output electric powers A and B, whose voltages are divided by resistors 51 and 52, and 61 and 62; and an abnormality discriminating part 8 compares them with data from a storage part 7. Once abnormality is discriminated, a switch part 2 is driven to cut off the power supply and make a display part 10 illuminate, and data showing the contents of the abnormality are read out of the storage part and sent out from an output part 11 to a personal computer 13 through a signal line 12, so that the contents of the abnormality are displayed on the screen. The abnormality discriminating part, storage part, control part, display part, output, part, etc., operate with the electric power obtained from the commercial power source through the transformation and rectification of the power source part 4.