Comments on "Compatible High-Density Bipolar Codes: An Unrestricted Transmission Plan for PCM Carriers"

The basic code proposed in the referenced parep is identical with a three-zero substitution code proposed previously, and the remaining codes are variants obtained by adding one or more zeros in front of three-zero substitution kernels. The bipolar with six-zero substitution (B6ZS) code is superior in baseline wander performance to codes based on the three-zero substitution kernels, and other differences in performance are small.