The double‑resistor principle advances the modular system—enabling higher load currents and larger step voltages.
After the lower to medium switching capability range of type D and its derivatives had been replaced by Types M and MS, Type T was developed to also replace the higher current variants of the Type D family.
In contrast to Type M, Type T was implemented using the double resistor switching principle, which made it possible to achieve both higher load currents and higher step voltages. Similar to the development of the Type M, the aim for the Type T was both a largely modular system and the introduction of glass fiber reinforced composites as insulating material in the diverter switch. The implementation of the request for plastic composites was carried out in stages, as with type M.