1885–1886. Additional dwellings, boiler and engine houses, a workshop and a coal store were built from the lighthouse in a small valley containing a fresh water loch. The engine house was fitted with two steam-powered generators, at 4.5 tons each the largest ever constructed at that time, and with a total output of 8.8 kilowatts. These powered an arc lamp in the lighthouse, with a three-wick paraffin lamp kept lit but turned down in case the electric lamp failed. The new light was first used on 1 December 1886 and produced four flashes every 30 seconds. The high cost of the coal, around 150 tons per year, along with improvements in oil lights led to the replacement with an incandescent mantle in 1924. Another smaller lighthouse, the Low Light was constructed a few hundred yards from the main light in 1843 to provide (with the main lighthouse) a pair of lights which would become aligned to help ships avoid the North Carr Rock to the north of the island off Fife Ness. It was first used in April 1844, but is no longer used, having been made redundant by the establishment of the North Carr Lightship in 1887 and the building is now used for bird watching. In 1930 two keepers rescued four crew members of the wrecked commercial trawler George Aunger by swimming out to it. The lighthouse became a "rock" station on 9 August 1972, meaning that the keeper's families were no longer accommodated at the lighthouse but on the mainland, and a fully automatic one on 31 March 1989 shortly before ownership of the island passed to the Nature Conservancy Council. It is now monitored and controlled via a UHF radio link to Fife Ness Lighthouse and then by landline to the Northern Lighthouse Board headquarters in Edinburgh. The modern light produces two white flashes every 15 seconds, and has a range of in good visibility. The fog signal, from two designated buildings at each end of the island, were powered by compressed air, generated from the island's power plant in the centre of the island, and delivered by cast-iron pipes laid on the ground to top up a series of air tanks located adjacent to both North and South buildings. The North horn provided a single blast of 7 seconds duration every 2 minutes and the South horn provided four 2 second blasts of the same