The Aldis Lamp: Morse in Light Between Ships The Aldis lamp turned flashing light into a naval language that radio silence cannot jam. This guide covers its optics, procedure and modern survival. Quick facts Optical core concave mirror Trigger action tilts the mirror Procedure call, answer, send Users ships + airfields Still used for silent signalling Because a lamp signal is directional and leaves no radio trace, navies kept the Aldis long after voice radio became universal. Harbour entries, emergencies and exercises still pass in flashes - Morse by daylight and by dark. Keep learning - text to morse code converter: Morse Code Works - free Morse code tools and guides. Reference chart