Ardois system

== English == === Etymology === (This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.) === Proper noun === the Ardois system (historical) A system used by the US Navy in the late 19th century to enable ship-to-ship communications at night. Each installation used a series of eight double lamps (four red and four white) hung from a mast and used to transmit visual codes.