These are on a few wooden poles in older Boston neighborhoods and these lights denote a fire alarm box located right below. These "radial wave" fixtures were made by the Wheeler Reflector Company and are slowly disappearing. They are mounted on standard 6-foot long street light brackets (some of them are ornate) and are about 20-25 feet above the pavement. Some of the "newer" fixtures have a transparent red plastic lens like a regular yard or security light....yet still incandescent!