A main control device generates a first signal and a second signal, which is substantially equivalent to the first signal, in accordance with the input signal, a sub-control device includes a comparison-judgment-processing unit that compares the first signal with the second signal, and judges that an abnormality occurs when a state, in which a deviation between the both signals is greater than equal to a predetermined value, is continued in a time being equal to a first predetermined time, and a limitation unit is configured in such a way that the limitation unit adds a predetermined limitation to the output of the main control device in accordance with a result for which the comparison-judgment-processing unit judges that the abnormality occurs.