Before radio, visual line of sight signalling with signal lamps, flags, and these physical semaphore devices were used. The concept of signaling for long distance communication is ancient and used extensively during earlier conflicts like the Napoleonic era. A version of semaphore devices survived in modern time in the form of railway signals. #WW1 #WWI #ww1history #logistics #capcut | This Day In WWI

Lesson: How to use semaphore flags | Oak National Academy