Implementation of the Fixed and Flashing Rhythmic Character on AtoN Lights

摘要

The fixed and flashing rhythmic character for navigational light signals combines the continuity of a fixed light marker with the conspicuity and lower power consumption of a higher intensity flashing light. It has been known already since the early 19th century (introduced by Augustin-Jean Fres-nel (France) and further described in 1881 by William Thomson (Lord Kelvin) in the paper "On Lighthouse Characteristics") and is currently listed in the IALA Recommendation E-110. Table I, as class 9, abbreviation FFI. In accordance with this recommendation, the duration of an FFI flash should be equal to or shorter than I second, while the low luminous intensity fixed light signal is provided during a time at least three times of the flash (d 3 I). Implementation of FFI character with a relatively long duration of the low intensity light signal phase ("low-lit eclipse") is reasonable; it would not be substantiated in case of short eclipses - a mariner would not lose the track of an AtoN signal during a short eclipse, while from the other hand, the eye would not adapt quickly enough to make use of the low intensity signal of short duration between flashes of higher luminous intensity in excess of an order of magni-tude.The key benefit of FFI implementation from the operational aspect is the ability to use a shorter flash phase and a longer low light signal during an eclipse without compromising navigation safety. Recent conversion of major lighthouses from rotating optics to LED lights that no longer provide a "halo" effect during an eclipse can be made much more acceptable to the mariners, even seamless, by replacing the former atmospheric effects of the rotating light beam by introducing a low light eclipse of an FFI rhythmic character.%Le feu fixe et à éclats, introduit par Augustin Fresnel, est mentionné dans la Recommandation E-110 de l'AISM sous l'abréviation FF1. Il alterne l'émission continue d'une lumière de faible intensité avec l'émission d'éclats de plus forte intensité lumineuse, selon un rythme déterminé, permettant au navigateur de ne jamais le perdre de vue. Ce type de feu n'est toutefois pas très populaire auprès des services de signalisation maritime, qui ont tendance à l'ignorer. Pourtant, alors que de plus en plus de phares sont équipés de LEDs, il présente un intérêt tout particulier. En effet, les LEDs ne produisent pas le « halo » qui nimbe les feux traditionnels pendant la durée de l'éclipsé et l'œil du marin perd totalement la trace de l'aide pendant cette durée.