Constrained codes have been mainly used in data storage media, such as CD's or
DVD's. The study of one-dimensional constrained codes is based on the study of
Shannon covers of sofic shifts. However, while a Shannon cover is well studied
when a sofic shift is irreducible, non-trivial properties for a Shannon cover
for a reducible sofic shift have not been analyzed up to this point. In this
talk, we will focus on some special reducible sofic shifts and consider useful
properties of their  Shannon covers.