| 摘要 |
<p>A lighting power monitoring system detects the availability of a normal or abnormal mains supply at a mains input (5) to enable activation of an emergency lighting mode in dependence thereon. The system includes a low-pass filter (21) coupled to the mains input (5) for producing a low-pass filtered output (23). Emergency lighting mode detection means (25) is arranged to generate a status signal "Out" indicative of the normal or abnormal status of the mains input. The status signal can be applied to an electronic controller (15) to control a lighting system in an optimised way in dependence upon whether the mains supply is normal or abnormal. A normal mains supply may be an AC mains supply and an abnormal mains supply may be a mains supply which includes a DC component.</p> |
