A GDT is basically a spark gap in a controlled environment. The standard construction of a GDT is a stacking of components which are then sealed to control the area of conduction. The ceramic tube provides high insulation resistance and low dielectric loss for the tube. The electrodes are typically either copper or a special Nickel/Iron alloy which are hermetically sealed to the ceramic with the braze alloy. Geometry/gradients of the electrodes improve turn-on characterization. Interior coating on the electrodes lowers electron work function, which results in less heating during surge and also improves gas purity, resulting in longer, more stable life. Bourns typically uses Argon and Neon gases in its GDTs and field enhancing lines of graphite are used to channel ionization and improve turn-on characteristics. Bourns uses high quality ceramics and electrode materials to provide the most stable, long life GDT possible. The proprietary formulized emission coating or “secret sauce” on the electrodes is the final ingredient which gives the Bourns® GDT its long life and stable performance.