You want to send a message to someone. Immediately. No problem. You just pick up a land phone or a mobile phone, or send an email. The telegram is still there but many of us have forgotten about it.
Now travel back in time to France, 206 years ago, when there was none of your latest technology. Not even the telegraph. But people still felt the need to send long distance messages.
It was then that a Frenchman called Chappe invented a code for the alphabet. It was called the semaphore. It was a code in which different positions of the human arm stood for a particular alphabet. Thus, there were 26 positions. People sent messages in this way by holding a flag in each hand to make sure that the positions were seen clearly, and a correct message was sent.
Later, an instrument with two mechanical arms was also used to send messages. The instrument was named semaphore after the code. It is used at sea to this day.
Then, it was the turn of the semaphore to be used for railway signals. It was used as a railway signal for the first time 159 years ago, in 1841. A signal arm in a horizontal position indicated that the driver must stop. A halfway down signal told the driver to move carefully till the next signal. A signal straight upwards told the driver that the way was all clear. The signals were painted red.
The semaphore was a great advancement on the early railway signals. A ball and a cloth kite was used for the purpose. A kite taken to the top of a pole meant danger. A ball on top of the pole meant a go-ahead signal.
With the invention of electricity, the railway signals also got electrified. A red light meant ‘stop’, amber meant ‘be careful’ and green meant ‘go’. This became the code everywhere.