Signal posts have been found along the Dutch coast for centuries. Since the 16th century there were lookouts on high dune tops or, as in Zeeland, on church towers. Often they served as beacons for fishermen along the coast. Sometimes also to warn coastal inhabitants of attacks from the sea. Between 1799 and 1813, these signal posts were equipped with coastal telegraphs or semaphores. A signal system that could relay messages with visual signals in case of an attack from the sea. In IJmuiden, the Seinpost post, together with the small and large lighthouses, which together form a line of light to mark the harbor, formed the main means of communication with shipping.