Abstract: A switch for use in transformer tap changing is modular in design, having standardized fixed contact units mounted in alignment on a base. Each contact unit has an electrical contact embedded in an insulating body, with a hollow bore formed through the insulating body and the embedded electrical contact. A cylindrical movable contactor having spaced contact bands is mounted on a shaft to be driven through the hollow bores of the fixed contact units between positions at which its contact bands engage the electrical contacts within adjacent fixed contact units. The electrical contacts of the fixed contact units are connected to different taps of the transformer to allow the transformer turns ratio to be adjusted by changing the position of the movable contactor. The drive shaft is connected by a mechanism to a handle mounted outside the tank of the transformer that can be operated to move the movable contact a selected distance to change the tap connections to the transformer.