| 摘要 |
The outdoor light has two identical discharge lamps (31, 32) and a bistable switch (4) with changeover contacts (41, 42), between the ballast device (2) and the parallel discharge lamps. The switch is in parallel with the series combination of changeover contacts and discharge lamps. Alternatively, the switch may be in parallel with the series combination of ballast device, changeover contacts and discharge lamps. The switch may be pulsed relay with a PTC resistor (5) on its excitation circuit. The switch and its contacts ensure that when one lamp reaches the end of its lifetime the other lamp is switched in thereby doubling the time between servicings (i.e. lamp replacement). Alternatively the lamps may be switched in and out alternatively until the lifetimes of both are reached roughly simultaneously. |
