  We study the problem of characterizing when two memoryless binary asymmetric
channels, described by their transition probabilities $(p,q)$ and $(p',q')$,
are equivalent from the point of view of maximum likelihood decoding (MLD) when
restricted to $n$-block binary codes. This equivalence of channels induces a
partition (depending on $n$) on the space of parameters $(p,q)$ into regions
associated with the equivalence classes. Explicit expressions for describing
these regions, their number and areas are derived. Some perspectives of
applications of our results to decoding problems are also presented.
