| 摘要 |
A lighting system 10 comprises an electricity supply 13, an illumination unit 12, a controller module 16 which controls the supply of electrical energy to the illumination unit and a light sensor 17 to sense the ambient light level and provide information indicative of dusk and dawn conditions. The controller module comprises a memory 20 to store information received from the sensor during at least one preceding twenty-four hour period in respect of the dusk to dawn duration and employs that information for controlling the time and/or the rate at which electrical energy is supplied to the illumination unit during the next dusk to dawn period by comparing the stored duration with a reference period stored in a reference time store 22. When the dusk to dawn period is less than the reference period the controller module causes the illumination unit to operate at a selected level of illumination throughout the reference period and when the dusk to dawn period is greater, the illumination unit is caused to operate for an intermediate period, between initial and final periods of the dusk to dawn interval, at a level of intensity which is less than the level of illumination at at least one of said initial and final periods. |
