Abstract: A fitting for the electrical connection and support of compact electric-discharge lamps of different powers and construction. An electrical series impedance device for the normal operation of the lamps is accommodated in the fitting. These devices also include a resistor (47, 48) which is responsive to the glow current of the lamps and which is arranged to maintain the glow current in the various lamps to which it may be fitted at substantially one and the same level. This is achieved by the fact that the resistor is temperature-responsive and is placed in good thermal contact with a distinct heat source, for example, the series choke (38).

Abstract: A fluorescent lamp has an envelope tube forming a gas-tight enclosure about a pair of externally-energizable filaments which generate a plasma discharge for conversion to visible light; a keep-alive electrode is located adjacent to at least one filament. A dimming control circuit individually externally energizes each keep-alive electrode to generate an auxiliary discharge, between that keep-alive electrode and the adjacent filament, at a magnitude sufficient to maintain the adjacent filament in the spot mode of operation even if the main plasma discharge current is varied over a range sufficient to change the visible light output of the lamp over at least a 10:1 range.