  We consider two systems of two conservation laws that are defined on
complementary spatial intervals and coupled by an interface as a single
port-Hamiltonian system. In case of a fixed interface position, we characterize
the boundary and interface conditions for which the associated port-Hamiltonian
operator generates a contraction semigroup. Furthermore, we present sufficient
conditions for the exponential stability of the generated $C_0$-semigroup. The
results are illustrated by the example of two acoustic waveguides coupled by an
interface consisting of some membrane.
