Gas discharge tubes (GDT), commonly known as lightning protection tubes or surge arrester , are packaged in ceramics hermetically with inert gases inside.

They are often used to protect sensitive circuit inputs from potentially damaging interference voltage transients. The large amount of energy that can be dispersed by gas discharge tubes makes them a good choice for lightning surge protection, particularly for telecommunications equipment. Its main feature: very high current handling capability, low capacitance, high insulation resistance, very high firing voltage, finite life cycle, slow response times.