Applies to three-pole units for public and industrial distribution systems which are functional assemblies of switches including switch-disconnectors and current-limiting fuses designed so as to be capable of breaking, at the rated recovery voltage, any current up to and including the rated short-circuit breaking current, making, at the rated voltage, circuits to which the rated short-circuit breaking current applies. It applies to combinations designed with rated voltages above 1 kV up to and including 52 kV for use on three-phase alternating current systems of either 50 Hz or 60 Hz.