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over-voltage An unusually high voltage. With many switching PSUs a single component failure can cause the output voltage to rise above that which the load can safely tolerate. This could destroy all the components connected to that supply. It is common to provide a special circuit which forces the output to a low voltage and will usually operate protective devices (fuse or overload relay), thus removing all power. This is sometimes called a crowbar circuit (equivalent to connecting a crowbar across the output terminals).