The Three-Phase Regulating Autotransformer consists of a three-phase autotransformer enclosed in a half-size EMS module. Eight safety banana jacks on the module front panel provide access to both sides of the regulating autotransformer. A buck-boost selector switch can be used to increase or decrease the autotransformer output voltage by 15%. A phase-shift selector switch can be used to set the phase shift produced by the autotransformer output voltage to ±15°. A phase sequence indicator on the module front panel indicates the phase sequence of the voltages across the autotransformer.