A transformer which incorporates the primary and secondary functions into a single winding, which is common to both input and output circuits, and is designed to change the relationship of volts and amperes between the entire winding and its taps. Includes multiple winding transformers of like design and items in which a variation of the turns ratio or inductive ratio of inductive coupling is accomplished by connection to fixed terminals. Also, includes items having a provision for mechanically changing the turns ratio in progressive increments, by means of a shaft, voltage taps, ratio adjuster, or devices of similar design. Excludes transformer (1), power; transformer (1), pulse.