  This paper is concerned with exponential stability of a class of infinite
dimensional coupled systems. It is proved that under some admissibility
conditions, the considered infinite dimensional coupled system is governed by a
$C_0$-semigroup. Furthermore, if both the free subsystems are governed by
exponentially stable $C_0$-semigroups, then so is the coupled system. The
results are applied to simplify the proof of semigroup generation and
exponential stability for several coupled systems emerged in control theory
literatures.
