SPDs and arrestors (lightning arrestors) are surge protection devices that prevent electrical and electronic equipment failures that can occur due to lightning. If lightning causes a transient overvoltage (surge) to enter the equipment, the electronic circuit will fail. SPDs and arrestors (lightning arrestors) work to protect precision equipment, etc. by controlling transient applied voltages that occur momentarily. The SPD and arrestor (lightning arrester) work to bypassed and escape the surge to the earth. Zinc oxide elements are mainly used to absorb lightning surges, and in addition, silicon elements, molybdenum elements, gas tube elements, etc. are combined to make the products. The type varies depending on the application, such as for equipment, for power supplies with fuses, for power distribution board, for signal lines, etc. In addition, there are various features such as types with excellent responsiveness and durability, non-continuous types, compact types, etc.