An electric discharge lamp with an ion reservoir to which a DC voltage of reversible polarity is applied so that the gas pressure within the lamp can be easily increased or decreased. By using several ionizable materials in the lamp, the color of the emitted light can be changed by adding or removing one of said materials.
The invention relates to a device for operating a low-pressure sodium vapor discharge lamp without a stabilizing ballast. The lamp is provided with a discharge tube having first and second main electrodes opposing a third main electrode. An automatically operating change-over switch occasionally switches the lamp current to either the first or second electrodes. A reservoir of liquid sodium near the first electrode affects sodium vapor pressure in the discharge tube by the switching action.
