English: Each of 3 pairs of graphs depicts the spectral distributions of an oversampled function and the same function sampled at 1/3 the original rate. The bandwidth, B, in this example is just small enough that the slower sampling does not cause overlap (aliasing). The top pair of graphs represent the discrete-time Fourier transform (DTFT) representation. The middle pair, depict a normalized frequency scale, preferred by many filter design programs. The frequency, f, in Hz is divided by the sample-rate. The periodicity and Nyquist frequency are then represented by constants, 1 and 1/2 respectively. The bottom pair depict a different normalized frequency scale, used by the Z-transform... the periodicity and Nyquist frequency are respectively represented by 2π and π.