# Translations:Frequency response of a digital system/42/en

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In Figure 10, we show the angle for various points on the unit circle. We trace out one period of the frequency function if we travel counterclockwise around the unit circle from point *A* to *B, C, D, E*, and back to *A*. Over this journey, we see that the angle increases monotonically from 0 to . Thus, the given factor of a dispersive all-pass system produces an increase in phase lag of over one complete period of frequency Therefore, a dispersive all-pass system of *q* such factors would have a phase-lag spectrum that increases monotonically by an amount over one complete period; that is,