A general scheme for DC-free (d,k)-constrained block codes is considered. In this scheme, messages are mapped to nonzero dklr-sequences of fixed length. For any two dklr-sequences, two merging sequences of fixed length and of different weight parities are available such that each one of these sequences can be inserted between the two dklr-sequences to maintain the (d,k) constraint. One of these two merging sequences is chosen to ensure that the code is DC-free. For all (d,k) constraints with capacities at least equal to 0.5, optimal values of l and r that yield maximal code rates are specified.
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