Abstract: A regulating transformer including a base winding and a plurality of auxiliary windings adapted to be connected in whole, or in part, to said base winding. The ends of each auxiliary winding and a point between its ends are passed through a bushing to a change-over switch arranged outside the transformer tank. The base winding of the transformer is connected to the movable contact of a first change-over switch. The movable contacts of continuous change-over switches are interconnected. The movable contact of the last change-over switch is connected to an outgoing line. Each change-over switch has a movable contact that can be selectively engaged with either of a pair of fixed contacts. One of the fixed contacts is connected to one of the ends of an auxiliary transformer winding. The other of the fixed contacts is connected to a point, or tap, between the ends of the auxiliary winding.