Parallel communicating grammar systems with separated alphabets

The generative capacity of parallel communicating grammar systems is considered in the context that the component grammars have distinct terminal and nonterminal sets. In the regular case, this results in strictly more powerful systems in comparison to the classical ones. In the context-free case, characterization of recursively enumerable languages is obtained when A-rules are allowed in non-centralized returning systems, deriving in the synchronized mode. Unsynchronized context-free systems with separated alphabets have the same power as the corresponding usual systems