Automatic lamp changer

An automatic lamp changer (or lampchanger) is a device used to ensure that a navigational light such as a marine lighthouse or aero beacon stays lit even if a bulb burns out.

The common design elements are an array of two or more lamps (or bulbs), installed on a mounting which can rotate to various positions.

Each position brings a different lamp into the focal point of an optical assembly.

Since signal and navigational lights use sophisticated optics to focus the beam, lampchangers are designed to position the new bulb at the focal point with high precision.

The United States Lighthouse Service had these in common use by the 1930s, as they moved to convert all navigational lights to electricity.