Among the protective devices, the gas discharge tube is characterized by large flux, but slow response time, and high impact breakdown voltage; TVS tube has small flux, fastest response time, and best voltage clamping characteristics; characteristics of varistor Between the two, when a protection circuit requires a large overall flow to achieve fine protection, the protection circuit often requires the combination of these types of protection devices to achieve relatively ideal protection characteristics. However, these protective devices cannot be used in parallel. For example, a varistor with a large flow rate and a TVS tube with a small flow rate are directly connected in parallel. Under the action of an overcurrent, the TVS tube will be damaged first, and the varistor cannot be used. The advantage of large traffic. Therefore, when several protection devices are used together, inductance, resistance, and wires are often required to cooperate between different protection components.