Patent ID: 7102289

Claim:
A discharge tube, comprising: an airtight tube formed of an insulator, the airtight tube having an inner wall surface and first and second end surfaces having first and second metallized surfaces, respectively, formed thereon; a first discharge electrode joined to the first metallized surface formed on the first end surface of the airtight tube; a second discharge electrode joined to the second metallized surface formed on the second end surface of the airtight tube; and a plurality of trigger lines formed on the inner wall surface of the airtight tube so as to extend in axial directions of the airtight tube, wherein: the first and second discharge electrodes are joined to the first and second metallized surfaces so that a discharge gap is formed between the first and second discharge electrodes and the airtight tube is hermetically sealed; and the trigger lines include at least one first trigger line connected to the first metallized surface and at least one second trigger line connected to the second metallized surface, the first and second trigger lines being separated from each other around the inner wall surface by a first distance, and a plurality of third trigger lines out of contact with and isolated from the first and second metallized surfaces, and each adjacent two of the third trigger lines are separated from each other around the inner wall surface by a same second distance that is different from the first distance.