The Netherlands, Belgium and Scandinavia

Recent research into the history of time signals in the Netherlands and Belgium has exposed time signals that appear to have been unknown to the British Admiralty in their early years. Time discs, often called flaps or boards, became the preferred signal in the Netherlands after 1854, superseding time balls that were first dropped from guard ships at Hellevoetsluis and Nieuwe Diep in 1846. From a distance, discs rotating about a horizontal axis looked like a disappearing time ball. They were usually perforated to reduce aerodynamic drag and weight, allowing operation in high winds as well as rapid rotation to reduce signal ambiguity. Antwerp introduced a time ball in 1856, superseded by time discs in 1883. Time balls and drums were used at many locations in Scandinavia and time lights were introduced in the Netherlands and Norway after 1919. Time guns were never listed. The first Scandinavian time ball was introduced at Copenhagen in 1868, replacing a flag signal.