Abstract: An in-line buck/boost voltage/regulating apparatus and system for delivering AC electrical power of regulated voltage from an output terminal of a main winding to an electrical load. The apparatus has an input terminal for connection to an AC power supply and comprises first, second and third ferromagnetic transformer cores having first, second and third cross-sectional areas, respectively; and these cross-sectional areas have relative sizes of X square units, Y square units and Z square units, respectively. There are first, second and third regulator windings respectively mounted on the first, second and third cores, and electromagnetically coupled with their respective cores. The first, second and third windings have first, second and third numbers of turns, respectively. Switching elements selectively connect the first, second and/or third windings across the AC supply and selectively short-circuit any of the first, second and/or third windings which are not connected across the AC supply.