The product is special auto transformer which is connectded in different forms. Its outputvoltage can be regulated smoothly and continuously from zero to the maximum value. Theprovision of an indicating meter is made for the models TDGC0.2, 0.25, 0.5/0.5(M). All themodels find popular applications in industries, agriculture and scientific researches, and areparticularly suited to servs as ancillary facilities for such equipment as various machine tools, transistor curve tracers, projecting TV sets, and analytical instruments in petroleum industry, etc.