An Aldis lamp is a small handheld lamp which has a trigger operated shutter that was used to send Morse Code messages between ships, or from ships to shore. The Aldis Lamp was omnidirectional and good to use because it was hard for enemy ships to pick up the signal, a ship would have to be reasonably close to see it.
The idea of using flashing lights to send out a code was first implimented by Philip Colomb in 1867. The Navy used his code for 7 years and then switched to Morse Code. The Royal Navy used it as well, but had primarily used flags to get codes across. Some large ships are still equipped with Morse Code devices, but they have been completely phased out by the navy of most countries in lieu of more sophisicated equipment.For quotes and more information see: