flaggsignalsystem

Flaggsignalsystem, literally "flag signaling system," is a term used to describe organized methods of communicating information visually through flags or pennants of different colors, shapes, and patterns. Historically developed for maritime and military use, flag signaling systems enable messages to be conveyed over line-of-sight distances without electronic devices. The term covers several subsystems, the most prominent being the International Code of Signals (ICS), a standardized set of nautical signal flags, and the separate semaphore system in which a person holds two flags to form letters and numbers.

The International Code of Signals assigns meanings to individual flags and supports combinations to spell words or indicate procedural signals such as distress, weather, or maneuvering instructions. Semaphore signaling uses fixed flag positions for each letter and numeral, allowing quick manual signaling in calm conditions. Other flag families include national or service pennants and specialized flags that convey status, safety, or authorization.

In modern times, flag signaling remains part of seafaring education and is retained for ceremonial use, recreational boating, and certain rescue or training operations where radio silence is required. Its practicality is limited by weather, light, distance, and wind, but it continues to provide a robust, equipment-free means of communication when line-of-sight is available.

See also: maritime signal flags, semaphore, International Code of Signals, nautical signaling.