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dual headlighting system

[11.6.1.5] In vehicle lighting: Two double headlighting units, one mounted on each side of the front end of a vehicle. Each unit consists of two sealed beam lamps mounted in a single housing. The upper or outer lamps have two filaments, which supply the lower beam and part of the upper beam.The lower or inner lamps have one filament, which provides the primary source of light for the upper beam.

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