GDT( Gas Discharge Tubes), is airtight device consisting of one or more discharge gaps filled with inert gases. The electrical performance of GDT depends on the type of gas, gas pressure, internal electrode structure, fabrication process and other factors. When the voltage added to the two electrodes reaches the breakdown point of gas in GDT, the discharge begins, which changes from high impedance to low impedance, makes the surge voltage short-circuit to near zero voltage quickly, and releases the overcurrent into the ground, finally to protect the subsequent circuit.

GDT can withstand surge current shocks up to tens or even hundreds of kiloamperes, and has very low junction capacitance. GDT is the used widely switching component in lightning protection equipment to protect electronic equipment and human body from the harm of transient high voltage. The surge current of GDT manufactured by DOWO can reach 20KA, 40KA, 50KA, 60KA, 100KA, 150KA ,or even higher; the insulation resistance can reach 10G; and the interelectrode capacitance is as low as 1PF. So, GDT is widely used for lightning protection in communication lines, security units of communication wiring frame and high frequency circuits.