Semaphore

Semaphore (lit. 'apparatus for signalling'; from Ancient Greek σῆμα (sêma) 'mark, sign, token', and Greek -φόρος (-phóros) 'bearer, carrier') is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arranged in visually connected networks, or for traffic signalling such as in railway systems, or traffic lights in cities.