It is a smart idea to protect the connected devices within your home or work environment. Electrical equipment may be damaged if exposed to voltages greater than 1.5kV.
So in the event of a lightning strike the appliances connected within your home are protected from a voltage surge. CSG range of surge arresters housing cradles are 35mm DIN rail mount and replacement modules are manufactured using metal oxide resistors designed to suppress dangerous voltage.
They come with an indicator that alerts the occupant when the module needs replacing.