| 摘要 |
Illuminated warning signs of familiar shapes employ back lighting through letters of smoked translucent plastic or glass. The back lighting is produced by incandescent lights or light emitting diodes located behind the letters. Thus, for example, in daylight a stop sign will appear to have black or white letters in contrast to the red background of the stop sign, but at night the letters will glow. Since warning signs provide shape to indicate the nature of the warning, the perimeter of the sign is likewise caused to glow brightly by providing one or a plurality of light pipes illuminated by lamps or a plurality of light emitting diodes. Thus, the combination of the word and the perimeter glowing brightly make clear the nature of the warning despite the sign being otherwise obscured.
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