Modern Semaphores
The first passenger-carrying railroads began operating in the late 1820’s. It wasn’t very long before people realized that some sort of signaling was necessary to protect trains from crashing into each other.
At first, policemen stood at crossings and junctions and used hand held flags to signal passing trains. They were acting like human semaphore poles, with their two arms holding flags that signified clear messages.
A red flag meant “Danger”, a green flag, “Caution” and a white flag, “Clear”. None of this was very helpful in foggy conditions or in the dark of night. So the policemen used hand lanterns with colored lights in order to be seen. Later, all the policemen, flags and lanterns were replaced by posts with arms. Sound familiar? These posts were much like the ones the Chappe brothers had invented. Arm positions and colored boards gave a clear message during the day. Lanterns hung on the posts were used at night. With the advent of electricity the posts and lanterns were replaced by signals like the ones we use at traffic stops today. Red was still “danger” or “stop”, but now yellow became “caution” and green gave the “all clear”.
Over time semaphore has come to mean not only the exact system the Chappe brothers invented, but others too. For instance, sailors have two semaphore systems. They can signal by using hand held flags. The position of their arms holding the flags indicates the letter of the alphabet and they can be seen as far as 600 yards away during the day. Sailors also signal using a huge electric lantern with shutters. By opening and closing the shutters at different intervals they can send complex messages day or night. Kind of reminds you of the ancient Greeks with their mirrors, except that you don’t need the sun to flash a message. Both the old and new train signals are semaphores and even a modern traffic signal is considered a semaphore. And all because two brothers wanted to communicate with each other!
