DC spark-over voltage：The voltage at which the ceramic gas discharge tube sparks over with gradully increasing DC voltage.

Impulse spark-over voltage: The highest voltage at which the ceramic gas discharge tube sparks over with given ware-shape at a rise speed 1000V/μs, and it is also called as “pulse voltage".

Holdover voltages : The maximum DC voltage across the terminals of a ceramic gas discharge tube under which it may be expected to clear and to return to the high impedance state after the passage of a surge, under specified circuit conditions.

Alternating discharge current : The r.m.s. value of an approximately sinusoidal alternating current passing through the ceramic gas discharge tube.

Impulse discharge current: The peak value of the impulse current passing through the ceramic gas discharge tube, and it is also called as pulse discharge current or surge discharge current, including 10/1000μs long-wave discharge current and 8/20μs short-wave discharge current.

Insulation resistance：DC resistance of the gas discharge tube under specified conditions. Test voltage must be lower than DC spark-over voltage.

Inter-electrode capacitance : The capacitance between any two electrodes in the gas discharge tube. Its value is mainly determined by the size of electrode and distance between electrodes. In addition, the capacitance is also related to the lead wire length, spacing and dielectric in the ceramic gas discharge tube.