Types 1

There are 3 types of lights used as aids to navigation:
Alternating lights, Sector lights, and Range lights.
Alternating lights are used when great caution is required, for example when entering a harbor.
The light alternates color, for example Alternating White and Red.
Sector lights are used to point out hazards to navigation and to warn the navigator as he is approaching the light from this specific sector.
The sector could be either a few degrees in width, marking a navigation hazard such as a shoal or a rock, or could be a sector which covers a wide range, marking a safe approach in deep water.
True bearings are used to form the limits of the various sectors, observed from a vessel that moves in a clockwise direction around the light.