  The possible functional forms of the effective conductivity sigma_{eff} of
the randomly inhomogeneous two-phase system at arbitrary values of
concentrations are discussed. A new functional equation, generalizing the
duality relation, is deduced for systems with a finite maximal characteristical
scale of the inhomogeneties and its solution is found. A hierarchical method of
the construction of the model random inhomogeneous medium is proposed and one
such simple model is constructed. Its effective conductivity at arbitrary phase
concentrations is found in mean field like approximation. The derived formulas
for the effective conductivity are different and also (1) satisfy all necessary
inequalities and symmetries, including a dual symmetry; (2) reproduce the known
formulas for sigma_{eff} in weakly inhomogeneous case. It means that in general
sigma_{eff} of the two-phase randomly inhomogeneous systems may be a
nonuniversal function and can depend on some details of the structure of the
randomly inhomogeneous regions. The percolation limit is briefly discussed.
