TSD (hanging type ) servo mode AC voltage stabilizer is developed on the base of SVC series high accuracy full automatic AC voltage stabilizer. Compared with the original product, this type possesses higher quality and more functions, novel and luxurious ap pearance, hanging type installation for requiring small area. It forms the control system with linear integrated circuit and logical circuit, and drives the contact type voltage regulator to regulating automatically by controlling the servomotor. It adopts high precision servo voltage stabilizing technology which usually is applied to industry for civilian industry product, to conquer the weakness of instantaneous power failure of traditional switching, and consequently realize highprecision and uninterrupted stable voltage output, when the voltage from outer power network is not stable, it also can guarantee the top grade electrical appliances work safely and normally and prolong their service lives effectively, it is really the only ideal protection product for household and imported top grade electrical appliances (power supply of 110V).