Specifics of The Light
The twelve metre high light has two double banked units of twelve lamps mounted facing in opposite directions, operated by an AGA PRB21 Gearless Drive Unit rotating at three revolutions-per-minute, giving a flash every ten seconds.
Only eight out of the twelve lamps (30 volts 200 watts) run at 25 volts 150 watts to give increased service life which are used in normal operation. The other four lamps are 6 volts 28.5 watts used only as emergency lamps. Such emergencies may be during loss of mains electric power or the unlikelihood of a complete failure of the main lamp banks.
The corresponding four emergency lamps are connected in series, if one lamp fails all four go out, which gives each unit the same intensity, similarly with the 6 volt lamps of power. Power is provided by emergency batteries. The emergency light is a 200 mm lantern mounted on the balcony rail.
Read more about this topic: Douglas Head Lighthouse
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