Abstract: In a method of dimensioning and operating by A.C. or D.C. at a predetermined external heater power a low pressure discharge lamp, particularly a fluorescent lamp having two electrodes between which the discharge is formed, at least one of the electrodes being alkaline earth oxide coated and adapted to form a permanently heated cathode, particularly for use in video matrix board, and external heater current is used which is approximately 1.5 to 5 times higher than the discharge current, the heater volt is approximately 33.33% to 80% lower than that of a conventionally operated cathode or electrode, respectively, and the wattage of the heater circuit is maintained. By this accuracy of optimum cathode temperature control is improved, enhanced lamp life and reduced discoloration are obtained and the formation of hot spots avoided.

Abstract: For far-reaching reduction of cataphoresis of a fluorescent lamp for unipolar mode of operation, the anode thereof is such that in order to decrease anode current density its surface effective for the formation of the electric field of discharge amounts to 60-100 % of the maximal cross-sectional area of the discharge envelope, measured vertically to the discharge axis. Suitably the anode is provided with heat dissipators to thereby obtain a still greater temperature gradient. A permanent external heating of the cathode permits a particularly good igniting behaviour and a simple luminosity regulation which are advantageous when the lamp is used for reproduction of alphanumeric characters and images e.g. in a matrix, a display or the like.