[en] This paper is concerned with the inverse electromagnetic scattering by a two-layered medium in the non-magnetic case. We prove that both the electric permittivity and the conductivity can be uniquely recovered in an unknown annular domain by the internal wave-field measurements at one fixed frequency, if and are both assumed to be constant. Furthermore, we prove that the unknown annular domain can be also uniquely recovered using the same measurements. The method proposed in this paper essentially depends on the uniform a priori estimate for the scattered magnetic field in the sense when the incident fields are induced by a sequence of deformed electric dipoles. Another important ingredient for our method is to reconstruct well-defined PDE systems in a sufficiently small domain by using the solutions to the electromagnetic scattering problem in the two-layered cavity. (paper)