A low elevational profile of each of a pair of first and second wheel chocks for restraining a current \u201clow-drag\u201d motor vehicle in a carrier, such as a railway car, is derived from each wheel chock having an internally webbed, elongated stepped-box body terminated with a relatively short rectangular box having its inner wall integrally formed with the stepped-box body. Therefore, even if the cathode terminal is caused to be peeled off from the cathode portion, the peeling can be restricted to only one of the first and second flat portions, so that the peeled-off area can be prevented from increasing. Contact by one or more input mechanisms is detected in a region that corresponds to the first displayed object. The expander circuit having a variable gain amplifier includes a rectifier.