  Given an irreducible inclusion of infinite von-Neumann-algebras $\cn \subset
\cm$ together with a conditional expectation $ E : \cm \rightarrow \cm $ such
that the inclusion has depth 2, we show quite explicitely how $\cn $ can be
viewed as the fixed point algebra of $\cm$ w.r.t. an outer action of a compact
Kac-algebra acting on $\cm$. This gives an alternative proof, under this
special setting of a more general result of M. Enock and R. Nest, [E-N], see
also S. Yamagami, [Ya2].
