This series Constant Voltage Transformer(CVT) combines isolation transformer, bi-directional filter, and wide range voltage regulation, 3 functions integrated in 1. Isolating between input and output, high interference suppression for 3rd-13th harmonic, surge, rush and lightning pulses in main network. It is specially used for apparatus and instruments that are sensitive to heavy interference in mains. Its specification quality has been approved by space science and technical group for type test and environmental test. It has mentioned as special used in military.