The movable-shunt control is often used with a-c transformer-type welding power supplies. It may also be used with ac-dc power sources. The shunt acts to divert the magnetic flux around the coils. (In this usage, the term flux refers to the magnetic lines of force). In this design, the primary coils and the secondary coils are in fixed position. Control is obtained with a laminated iron core shunt that is moved between the primary and secondary coils. It is made of the same material as used in the transformer core.