RSC & RBO Ring Lug Terminal Blocks Phoenix Contact Open-Style Ring Screw (RSC) and Ring Bolt (RBO) Terminal Blocks have a compact, modular design with 9mm and 13mm profiles, and can replace traditional barrier blocks. Because the RSC/RBO ring terminals are smaller than most traditional barrier blocks, the density within the control cabinet is increased. Available in both DIN rail terminal block and panel-mount terminal block packages, the RSC and RBO terminal blocks can be assembled to support unique configurations. Phoenix Contact RSC and RBO terminal blocks are ideally suited for industrial control and switchgear applications.