An occulting light
is a rhythmic light
in which the total duration of light in each period is clearly longer than the total duration of darkness and in which the intervals of darkness (occultations) are all of equal duration.
The term is commonly used for a single occulting light that exhibits only single occultations which are repeated at regular intervals. It is normally used in light signals in lighthouses
and lighted buoys
. Different lighthouses have different frequencies and not all are flashing; mariners can find out which lighthouse they are near by the characteristic of the light signal.
Other types of rhythmic lights used by lighted aids to navigation are isophase light and flashing light.