The invention relates to a switch assembly (1), in particular a preselector, for a variable transformer (4) having a first winding (2) and a second winding (3) with a first and a second tap (3.3, 3.4), said switch assembly comprising: a first connection terminal (2.1) that can be connected to the first winding (2); a second connection terminal (3.1) that can be connected to the first tap (3.3); a third connection terminal (3.2) that can be connected to the second tap (3.4); a first, second, third and fourth fixed contact (5.1, 5.2, 5.3, 5.4); a vacuum interrupter (6); a first moving contact (7) that can be contacted selectively with the first or second fixed contact (5.1, 5.2); a second moving contact (8) that can be contacted selectively with the third or fourth fixed contact (5.3, 5.4), wherein the second and the fourth fixed contact (5.2, 5.4) are connected to the second connection terminal (3.1), the first and the third fixed contact (5.1, 5.3) are connected to the third connection terminal (32) the first moving contact (7) is connected to the first connection terminal (2.1) via the vacuum interrupter (6), and the second moving contact (8) is connected to the first connection terminal (2.1).