  Josephson junctions between a $FeAs$-based superconductor with antiphase
s-wave pairing and a conventional s-wave superconductor are studied. The
translational invariance in a planar junction between a single crystal pnictide
and an aluminum metal greatly enhances the relative weight of electron pockets
in the pnictide to the critical current. In a wide doping region of the
pnictide, a planar and a point contact junctions have opposite phases, which
can be used to design a tri-junction ring with $\pi$ phase to probe the
antiphase pairing.
