Each lighthouse will have a specific character, or pattern of the light, that is distinct from others in the area, so they can be told apart. It can be described with a few abbreviations, which are used on sea charts to identify the different lights. The abbreviation consists of three main elements: the type of light (e.g. flashing or fixed), the colour of the light, and the period of time for the cycling of the light pattern. The abbreviations used in the following tables are:
Type of light: F – Fixed (always on), Fl – Flashing (light on periodically, but off for a much longer period), Oc – Occulting (like flashing, but period of light is longer than darkness), Q – Quick light (flashing rapidly, more than thirty times a minute). If the flashing or occulting occurs more than once in a sequence the number of times is included in parentheses (e.g. Fl (2) means it flashes twice).
Colour of light: W – white, R – red, G – green, Bu – blue. For white-only lights this is left out. If more than one colour is included this means that different colours are displayed in different directions (e.g. a white light is visible when in safe waters, but green or red when in areas that might not be safely navigable).
Period: The timing of the cycle of the light pattern (e.g. Fl 10s means a flash occurs every ten seconds).
The following is a table from Wikipedia showing all the different light characters. Have a look at the original Wikipedia page to see animated examples of the different patterns.
