This could be set to flash which ensured that buoys could be distinguished from ships' lights and from each other. A later development was the sun valve which shut off the gas during sunlight.

*These additions have one obvious value, they work even in low visibility fog conditions, and the whistling buoys, on at least some models, work via the wave action acting as piston in an open-bottomed chamber with a whistle mechanism in fact making more noise the greater the water's hazards,