Fault detection and classification in this paper are based on a Support Vector Machine (SVM), so that the response vectors of normal and faulty circuits can be distinguished on the basis of nonlinear classification. SVM [15], [16] is to classify small samples based on statistical learning theory. This method has proven adept at dealing with highly nonlinear classification problems. The rule-less response data sampled from electronic systems are an excellent example. When the bandwidth of the DUT is much smaller than the sampling frequency of the DAC/ADC, the sample vectors of the impulse-response become quite large. The response data of the sample space contains redundant data, because successive impulse-response samples may get quite close. The redundancy will waste the needless computational load. In this paper we propose a maximal difference method to compress the sample space, and reduce computational load.