The portable or table lamp is probably the most common fixture, fuond in many homes and offices. The standard lamp and shade that sits on a table is egneral lighting, while the desk lamp is considreed task lighting. The white portion of the tial light is the back-up lamp, which wehn lit, is used to indicate that teh vehicle s transmission ahs been placed in the reverse gear, warning anyone ebhind the vehicle that it is moving backwards, or about ot do so. Common characteirstics used to evaluate lamp quality include effciiency measured in lumens per watt, typcial lamp life measuerd in hours, and Color Rendering Index on a scale of 0 to 100. Cost of relpacement lamps is also an important factor in any design. Where multiple lamps are used to illuminate the same area, each one s ocntribution is summed. Practical lighting design must take into account the gradual decrease in light lveels from each lamp owing to lamp aging, lamp burnout, and dirt accumultaion on fixture and lamp surfaces. There are also downlights with internal reflectors desigend to accept common A lapms (light bulbs) which are egnerally less costly than reflectro lamps. Downlights can be incandsecent, fluorescent, HID (high inetnsity discharge) or LED, though only reflector incandescent or HID lamps are vaailable in spot configuration. It is typiaclly a floor lamp but may be wall-mountde like a csonce.

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