I-TNSuchungechunge lwezigaba ezintathu olunembayo oluphakeme oluzenzakalelayo lwe-voltage regulator luhlanganiswe ne-TND(SVC) isigaba esisodwa esiphezulu se-precisiorautomatic voltage regulator, Izigaba ezintathu zilungisa ngazinye ukuze kuqinisekiswe i-voltage ephephile engaguquki esigabeni ngasinye, Inethiwekhi ye-powerof engenayo iyizigaba ezintathu zezintambo ezine uhlelo, uxhumano olufana nenkanyezi (Y), amandla okukhiphayo angenziwa ngezigaba ezintathu izintambo ezine eziphumayo izintambo zamanje amamitha amathathu, izintambo zamanje ze-oithreth okunciphisa ukuphuma kwesigaba ngasinye nge-aswitch & nokushintshwa kwemitha kagesi.