One of the last major uses of mercury arc valves was in HVDC power transmission, where they were used in many projects until the early 1970s, including the HVDC Inter-Island link between the North and South Islands of New Zealand and the HVDC Kingsnorth link from Kingsnorth power station to London.[11] However, starting about 1975, silicon devices have made mercury-arc rectifiers largely obsolete, even in HVDC applications.