Three electrode glass bulbs, gas filled, clean condition. When brought near the influence of a Tesla coil the bulbs fill with a purple discharge, and when a high voltage supply is connected across the leads purple bands form as shown in the photo. These could be some sort of high voltage arrester, or a three electrode trigger tube. The bulbs look to be in good shape with no silvering or other fouling of the glass.
If you ever thought two-electrode bulbs had 50% too few electrodes, this might be the item for you!.
|| 60 units in stock