Sorry.. I should have written an 'operational obstruction light'...
The raised jib is normal; raise to its highest possible position to reduce the oversail of the public domain...i.e foot paths and road below when not in use. This also reduces the moment arm the wind can generate at the tip, permitting slightly higher wind speed to be tolerated before the auto weathervaning operates. This will operate regardless of the crane being manned or not, with the human operator having only a little allowance to block it...