The ABB "D" series of tap changers and dual voltage switches are de-energized, rotary-type switches, suitable for use in distribution transformers, both pole and pad mounted. The switches are mounted through the tank wall and are operable from outside the transformer. They are available in single and multi-deck configurations with various types of coil lead connector styles so that they can be used in a wide variety of transformer applications. Ratings and performance features meet and often exceed the requirements of most transformer users.