Contraction rule provided by exponentials is the source of many troubles in linear logic. In particular, to prove undecidability of certain fragments of linear logic, commutative or non-commutative, one uses the whole power of recursive nature of the contraction rule. On the other hand, multiplexing rule has a very clear semantics, namely, !A provides at once any positive number of copies of A. Nevertheless, multiplexing and copying still provide undecidability. With multiplexing, however, there are simple syntactical restrictions that guarantee decidability.