Features:
1) The surge voltage caused by lightning on or around the external line
2) The short-time AC voltage inducted on external lines, when the power line, the power system or the electric railway system is broken down in the neighborhood of the external line
3) The external line directly collides against a 220V power line
4) Each protector has test eyelet, which can coordinate with the special test plug to test the external line as well as the components inside the protector

Technical specification:
1) Contact resistance difference between line and line: a??2Ic
2) Lower voltage limit:
a) GDT protector (100V/s escalating rate): a??190V
b) SA protector (100KV/s escalating rate): a??190V
3) Upper voltage limit:
a) GDT protector (100V/s escalating rate): a??260V, (1kV/us escalating rate a??800V
b) SA protectors (100KV/s escalating rate): a??260V, (1kV/us escalating rate) a??400V
4) Insulation resistance: a??1,000mIc (100V DC)