The integral characteristics of a poloidal divertor tokamak are investigated and the effect of a balancing magnetic field on the stability and shape of the plasma column is analysed. The formation of an ergodic layer near the separatrix in the presence of magnetic field perturbations is considered. On the basis of the calculations that are made, requirements are formulated for the accuracy to which the magnetic system must be produced, and a preliminary design of such a system for the TB-0 poloidal divertor tokamak is suggested.