11. Incandescent lamps were primarily used for street lighting until the advent of high-intensity discharge lamps . 12. Some gas-discharge lamps also have a perceivable start-up time to achieve their full light output. 13. Intensity control was provided via a mechanical shutter ( the discharge lamp being non-dimmable ). 14. Note that contemporary high intensity discharge lamps tend to use non-evaporable getters rather than flash getters. 15. Still, due to their greater efficiency, gas-discharge lamps are replacing incandescent lights in many lighting applications. 16. They may be as complex as the electronic ballasts used in fluorescent lamps and high-intensity discharge lamps . 17. A "'discharge lamp "'has a glass or silica envelope containing two metal electrodes separated by a gas. 18. High intensity discharge lamps have typical luminaire efficiencies of 55 %, and fluorescent lamps of 70 %. 19. High-intensity discharge lamps ( HID ) produce light with an electric arc rather than a glowing filament. 20. Sets of three high-intensity discharge lamps in the colors red, green and blue are mounted on the main cables.
