Otterblende
An otter screen is a component for beacons , named after its Swedish inventor, Baron Fredrik Wilhelm von Otter .
An otter screen consists of vertically arranged, opaque sheet metal strips, which are arranged like blinds in front of the lens and can be rotated by 90 ° in their longitudinal axis. Controlled by a mechanism, all strips are opened and closed in a certain rhythm in order to let the light through or to darken it. In this way they generate the identifier of the beacon . Today the screens are controlled by electromagnets and braked shortly before the stop so that there is no longer a hard stop, which used to cause the metal sheets to flutter. Baron von Otter presented his invention in Germany in 1878 on the Vareler Siel lighthouse . The Otterblende was first used in Germany in the Westermarkelsdorf lighthouse (1881) and the Roter Sand lighthouse (1885). The otter screen of the Dicke Berta lighthouse from 1897/1919 was operated with a pneumatic drive until 1983.
Since mechanical components are prone to failure, otter apertures are not used today as far as technically possible. Only a few lighthouses in Germany are still equipped with it, including the Baumrönne fire (canceled in 2011), the Arngast lighthouse and the Eckernförde lighthouse .