The magic is located in a small metal box with a glass lid mounted at the height of one of the lamps in a particular area. Inside is a very sensitive photoelectric cell that reacts in the absence of light. When it gets dark, the cell automatically closes the circuit, allowing power to flow and lighting a certain set of lights. When the first light from dawn appears, the "eye" opens the circuit, causing the lamp to go out. The amount of light or the absence of light needed to stimulate these cells can be changed from one facility to another to adjust various conditions in different regions; some roads receive direct light from the sun, while other roads are shaded by tall buildings or trees.
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