In this paper the problem of the parallel-plate waveguide with a ferrite substrate, having a semi-infinite upper plate and being excited by a TE mode is considered. The direction of the static(d.c.) magnetic field is taken to be parallel to the edge of the terminated upper plate. The problem is formulated on the basis of the Wiener-Hopf technique and ends up in a Wiener-Hopf integral equation with a non-symmetric kernel function, in contrast to the symmetric kernels of all isotropic problems formulated by the same technique. Factorization is now accomplished by a modification of the typical procedure, suitable to the present, non-syrmetric kernel. Expressions for the reflection and coupling coefficients of the modes are given and the far field is computed by application of appropriate asymptotic techniques. The numerical results reveal the definite possibility of controlling most of the operational characteristics of the structure by simply varying the intensity of the magnetizing field.