| 摘要 |
A switching control circuit for energizing a lamp in response to a decrease in ambient light below a predetermined level includes a photosensor and a timer circuit that responds to the photosensor indicating that the ambient light level is below a predetermined level by gating a solid state switching device into conductance to energize the lamp. The photosensor is powered by the signal that gates the switching device in a manner that renders the photosensor operative only when the lamp is not energized. Therefore, the lamp is energized upon the onset of dusk for a predetermined period of time during which the photosensor is disabled. After the period of time has expired, the lamp is deenergized and the photosensor is again enabled for a brief period of time to determine whether ambient light is still below the predetermined level. If it is, the light is again energized for another period of time. If not, the light remains deenergized. |
