The DC power industry offered stand-alone 200, 400 and 800A ferro-resonant rectifiers throughout the 1980s and 1990s. These legacy ferro-resonant rectifiers have since been discontinued by most manufacturers. The Ferro/SCR Retrofit Power Solution allows many brands and third-party legacy ferro-resonant rectifiers or SCRs to be upgraded to modern energy-efficient switch-mode rectifiers and controller technology, while preserving existing cabling and distribution investments. Bolting patterns remain the same as well.