Light characteristic

The abbreviation notation is slightly different from one light list to another, with dots added or removed, but it usually follows a pattern similar to the following (see the chart to the right for examples).

An example of a complete light characteristic is "Gp Oc(3) W 10s 15m 10M".

It is most commonly used for a single-flashing light which exhibits only single flashes which are repeated at regular intervals, in which case it is abbreviated simply as "Fl".

Like a flashing light, it can be used for a single occulting light that exhibits only a single period of darkness or the periods of darkness can be grouped and repeated at regular intervals (abbreviated "Oc"), a group (Oc(3)) or a composite group (Oc(2+1)).

The term occulting is used because originally the effect was obtained by a mechanism (e.g. a vertical or rotating shutter) periodically shading the light from view.

For example, "Al WG" shows white and green lights alternately.

Symbols and abbreviations for light characteristics
Flørauden seamark in Norway with its light characteristics and sector light
Clockwork occulting mechanism formerly in use at Coquet Island Lighthouse .