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By the way, a cold cathode fluorescent lamp is the best available source with respect to power consumption. Namely, the low power consumption enables use of the light source for notebook PCs without exception.
The filament lamp and electro-luminiscent foil are used in small scale applications as wristwatches and cellular phone displays.
Because the display lighting is only inter-mittently activated, the lifespan isn’t a subject to be solved so much, rather the cost for production is more important.
If a coloured backlighting is requested, light emitting diodes have a limited application.
