7.1 For the input sequence A _t of Example 7.1 (duobinary), show sequences B _t and C _t for the modified duobinary signal, using equations (7.8).

7.2 Suppose the initial digit in sequence B _t is 2 rather than 0 (Section 7.4). Write sequences B _t and C _t for this case. Verify that C _t assumes seven possible levels and that C _t mod 4= A _t .

7.3 The input binary data stream is such that p(1)= p(0)=1/2. For a duobinary correlative system with Q=4, what is the probability distribution of the seven levels ? What is it for the 7-level modified duobinary ?

7.4 Show that, in the 7-level duobinary or modified duobinary correlative system for Q=4, the extreme levels are formed in a unique way and that the intermediate levels may be formed in more than one way.

7.5 Derive the probability distribution of the nine signal states shown in Fig. 7.25.