Most primitive distance communications used visual devices that on a clear day could be seen up to 25 miles away.
If you wanted to send a message further than that, you needed a chain ...
Lines of beacons - substantial bonfires stacked on hills or on top of high towers - have provided an early warning message system for thousands of years. The Chinese, Egyptians and Romans all used beacon systems.
The most famous example from British history is the line of beacons set up along the southern coast of England in the year 1588 to warn us that the Spanish invasion fleet, the Armada, was coming.
When at last the great fleet appeared on the horizon off Cornwall, the fires on the hillsides were lit - sending the message to London faster than any horseman could ride.
Smoke signals were employed by Hannibal, the Carthaginian general who lived two centuries BC.
Roman sentries on Hadrian's Wall were often puzzled by the smoke signals used by marauding Picts - and the use of smoke by the Five Nations native tribes of America formed the stuff of many a good Western.
The advantage of smoke signals was that they could be used in wooded and hilly country - and could be seen more clearly on sunny days than signal fires. Also, by making smoke patterns (using a blanket over the fire) some coded messages could be sent. Sadly, these codes have long been lost.
Smoke flares are still used by military forces to communicate with friendly aircraft flying overhead and at sea to signal to rescue aircraft.
You can attract people's attention quickly, even a long way away, by reflecting the sun into their eyes with a mirror or other shiny surface. When you use this to signal messages, it's called a 'heliograph'.
The first recorded use of heliograph comes from 405 BC when the Ancient Greeks used polished shields to signal in battle. In about 35 AD, the Roman emperor Tiberius, by then very unpopular, ruled his vast empire from a villa on the Isle of Capri. It's thought he used a heliograph to send coded orders every day to the mainland, eight miles away.
The German Professor Carl Friedrich Gauss, of Goettingen University, outlined a first design for a formal heliograph in 1810. His device directed a controlled beam of sunlight to a distant station. It was meant to be used for geodetic survey work, but was later used extensively by the British and the American armies as a 'wirefree' field telegraph - using Morse Code.
The basic form of semaphore is a man waving his arms or flags in different patterns to represent letters and numbers. Using mechanical semaphore signals meant the shapes could be bigger - and seen further away.
Claude Chappe and his brothers developed a very effective semaphore system for France using chains of stations with rotating beams on masts to relay messages from one station to the next. He started this system in 1794 and it soon spanned Napoleon's empire.
The British Admiralty promptly developed its own system, using shutters, which it used to keep in touch with the main fleet bases at Great Yarmouth, Deal, Portsmouth and Plymouth.
These optical telegraphs were surprisingly quick - the noon time signal could be transmitted from London to Portsmouth (60 miles) in around 30 seconds. But the French semaphore telegraphs were better - because their signals were clearer and could be seen further away.
