2051 Series Gas Discharge Tube Surge Protector Bourns developed the 2051 Series Gas Discharge Tube (GDT) Surge Protector as an extremely small and robust overvoltage protection solution for telecom and industrial communications applications. Bourns offers the 2051 Series Gas Discharge Tube Surge Protector as a micro surface mount, 2-electrode GDT device designed to meet board-level protection requirements.