When a current spike or voltage surge suddenly occurs in an electrical circuit or a communication line due to external interference like lightning, surge protection device (SPD) can conduct the shunt in a very short time, thereby avoiding the damage of the surge to other equipment in the circuit. It is an indispensable device for lightning protection in the electronic equipment. But some people are still wondering why we need it, or whether need it when we have other lightning protection device? The following FAQ will give your answer for "Why you need a surge protection device".