A refrigerator includes a gas flow generator formed with passages providing communication between an annular inlet chamber and a gas flow chamber, so that gas under pressure in the inlet chamber flows through the passages into the gas flow chamber. The novel system includes subsystems for testing an automobile, or a part of an automobile, and comparing the result of the test with a baseline result. An abnormality triggered by a runaway of the sub-CPU can be resolved so that the sub-CPU can be restored to a normal condition as quickly as possible. The first and second multiplexing sections are provided between the optical fibers disposed between end offices.