This guide provides a comprehensive overview of semaphore, a signaling system used to communicate between two or more locations. It covers the history of semaphore, how it works, and how to implement it in various scenarios. It
From Wikipedia
Semaphore 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.