In this chapter, the authors aim to study the sampling process in a less precise setting. Of course, aliasing of signals will not occur if the highest frequency present in the sampled signal can be limited to the Nyquist frequency, which is determined by a suitable choice of the sampling rate. The cutoff frequency of the anti-aliasing lter can be set according to the sampling rate, so in theory no component with frequencies higher than the Nyquist frequency remains in the ltered signal, and no aliasing will occur in the reconstructed signal. In general, if a signal contains (higher) frequencies outside the Nyquist interval, they would be aliased to (lower) frequencies inside the Nyquist interval. When the original signal contains frequencies outside the Nyquist interval, their contribution to the sample values would appear as a contribution from lower frequencies in the signal reproduced from the samples.