Gas Discharge Tubes

Often abbreviated to GDT, gas discharge tubes consist of two or more electrons encased in an insulating temperature-resistant glass tube or bulb, which is then filled with a gas at less than atmospheric pressure. This device conducts electrical current after being ionised by a high voltage spike and effectively 'shorts' this power surge, thereby acting as a circuit protection device. Unlike other circuit breakers though, it will continue conducting until the current drops to normal levels. Gas discharge tubes are available in a number of varieties which are effective for different strengths of power surge. They are extremely versatile as devices since they can be used as a component in devices like surge protectors. Alternatively, they can be used alone to protect appliances, equipment or circuits. Some gas discharge tubes are designed to 'short' to a grounded terminal when overheated, rather like a circuit breaker. Apart from in surge protectors, gas discharge tubes can be found in power lines and telecommunications equipment, which are vulnerable to lightning strike as they are situated outside. They are also found in alarm systems, instrumentation circuits, outdoor power connections such as in gardens and electronic medical equipment.

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