The present invention is provided with a double filament and an electrode pin provided in the discharge tube, and the outlet support is provided with a separate spare pin hole in addition to the electrode pin hole by inserting the electrode pin in the electrode pin hole alternately to enable the use of the filament alternately As for;The primary electrode pin 4 and the secondary positive pin 5 are directly provided on the support 3 of the discharge tube 2 (2-1) provided with the primary and secondary filaments 6, 7 and the electrode The socket 12 is provided with electrode pin holes 13, 13-1, 13-2, 13-3 and spare pin holes 14, 14-1, or a protective cap 15. By inserting into the electrode pin hole 13, the primary and secondary filaments (6) and (7) can be selectively softened to extend the life of the discharge tube (2). Since it can be manufactured in the same process by the same method as it is to be equipped with a separate production equipment or can be easily manufactured without rising manufacturing costs.
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