Fig. 3 lightning protection of communication equipment

2) suppression circuit for gas discharge tube and a combination of varistor
Figure 4 is a combination of a gas discharge tube and surge suppression circuit composed of varistor. As the varistor has a fatal flaw: the leakage current is stable, the varistor poor performance after a period of time, due to leakage current increases may heat up. In order to solve the problem of the pressure sensitive resistor between the string into the gas discharge tube. However, the drawback is that the reaction time is the sum of the reaction time of the devices. For example, the reaction time of varistor is 25ns, the reaction time of the gas discharge tube is 100ns, while Figure 4 R2, G R3, the reaction time is 150ns, in order to improve the response time of joining the R1 varistor, so that the reaction time is 25ns.

3) applications of gas discharge tube in surge protection system in
The surge protection system required by the automatic control system is composed of two or three levels, which can be used to protect the reliability of the system. The gas discharge tube is generally placed in the input line, as the level of surge protection devices, bear big surge current. The two stage protection device adopts the varistor, which can respond more quickly in the s class time range. For highly sensitive electronic circuits, the three level protection device TVS can be used to generate a response to the surge voltage in the PS time range. As shown in figure 5. When the lightning surge arrives, TVS will first start, the transient overvoltage control at a certain level; if the surge current is large, varistor starter, and discharge the inrush current; the voltage will be increased, until the electric push put before the gas discharge tube, high current discharge ground.

　　Figure 5 level three protection