The RFP is believed to require a shell with high electrical conductivity very close to the boundary of the plasma. This requirement is an unfortunate complication in a reactor. The Madison Symmetric Torus was designed to test this assumption and to learn how good the conductor must be and how close to the plasma it must be placed. In RFX, the thick shell was replaced with an active system of 192 coils, which cover the entire torus with their saddle shape, and response to the magnetic push of the plasma. Active control of plasma modes is also possible with this system.