The approximate PSD is then evaluated by using Eq. (2-66) or, if the line code is periodic, Eq. (2-126). (Work Prob. 3-24 to apply this deterministic approach.) Alternatively, the PSD may be evaluated by using the stochastic approach that is developed in Chapter 6. The stochastic approach will be used to obtain the PSD of line codes that are shown in Fig. 3-15, because it gives the PSD for the line code with a random data sequence (instead of that for a particular data sequence).