It is well nigh impossible to describe the entire history of the electric telegraph in a few pages, but I hope we can still give you an insight into the ingenuity and technology of the early inventors - the pioneers who laid the foundations for today’s complex, computer based systems.
Since earliest times human beings have wanted to communicate at a distance. Primitive Man could keep hunting parties in touch about the movement of game by means of smoke signals. Military man was able to co-ordinate his armies. The ancient Greeks used mirrors to reflect the sun’s rays at the battle of Thermopylae.
All sorts of ways have been found of passing messages and they all rely on extending the human senses of sight or hearing in some way.
The explorer and journalist, Stanley, - famous for having found Dr Livingstone - when he was travelling the Congo river (now the River Zaire), was mystified to find that the villagers knew he was coming in advance. Of course the answer to the mystery was the talking drum. The drum is made from a tree trunk, hollowed out and shaped. Depending on how you hit it, different notes are produced which can sound like the local language. A means of communicating ideally suited to a country with dense forest, where one cannot see from one village to the next. Another very apt name for the drums is the ‘Jungle Telegraph’. Picture: Baptist Missionary Society
Conversely, one place where one can see for miles is at sea. And navies have used flags and semaphore for centuries. Using it on land is more difficult. To signal as far as possible some high vantage points are needed - even better if you can put it on a tower.
Just such a system was invented in the 1790s by Frenchman Claude Chappe - a system of wooden shutters on a tower, which could show 63 different signals. Naturally, military leaders quickly grasped the importance of systems like this and Napoleon made good use of the Chappe telegraph in his invasion of Italy. A system was made linking London to the naval dockyards at Portsmouth. Needless to say, fog or bad weather frequently interrupted communication. Picture: Deal Time Ball Museuem
[Watch this YouTube video of Prof Nigel Linge demonstrating a Chappe telegraph replica]
These semaphore type systems were the first to be described as a telegraph. Telegraph was a word coined in 1792 from the Greek, tele, afar, and graphos, a writer. Concise Oxford Dictionary
But electricity was on its way to assist the art of telegraphy. In the second half of the 18th Century there were important discoveries about the nature of electricity though it remained a mysterious fluid. Galvani conducted experiments with frogs’ legs to show the effects of electricity. Volta developed a battery, giving a steady source. Other experiments showed that transmission along wires was virtually instantaneous. This held out tantalising prospects for telegraphy. The first problem was to detect the presence of an electric current. Picture: Frog, BT; Galvani, unknown
Lesage’s telegraph used pith ball electrometers and another early idea
from S.T. van Soemmering was to use the electrolysis of water to detect
the current. But an important breakthrough came in 1810 when Ampere and
Oersted showed that the current in a wire could deflect a magnetised needle.
By 1836 a needle telegraph had been developed by Baron Pawel Schilling.
This was seen by the young William Cooke. Picture: Science Museum collection
Cooke immediately saw the possibilities of a telegraphic system linking the major towns in the country. But he was unknown to investors. So to get commercial support for his scheme he turned to Professor Charles Wheatstone as partner. It was in 1837 that Cooke & Wheatstone devised the first practical telegraph, which was known as the five needle system. This was an alphabetical system with five needles, controlled by five separate wires.
The needles pointed to to the desired letter. It only remained for the receiving operator to note down the letters in order as received.
[Watch this YouTube video of Prof Nigel Linge demonstrating a 5-needle replica]
The five needle system was clumsy to operate and, because it needed five wires, was expensive to cable. It was not long before it was replaced by the double needle system, with only two wires, using a code to indicate the letters. The first telegraphs were the Railway Companies’ private systems, but the double needle telegraph was the first to be used for a public telegraph from Paddington to Slough in 1841.
In turn the double needle gave way to the single needle system, using only one wire and the famous code developed by the American, Samuel Finley Breese Morse. A further development, the Highton single needle system, introduced in 1837 employed the Morse code, transmitted from a device known as a commutator. The commutator had two keys, which made current flow in opposite directions in the line, corresponding to a dot and a dash.
Originally, the receiving operator had to watch the needle and write down the letters. This made it very slow, and pretty soon means were found to make the signal audible to the operator. By putting two different type of stop pins, two distinctive sounds were made - a sort of ‘ting’ and ‘tong’. The operator now had only to concentrate on listening to the sounds, and write down the letters.
Experience soon showed that a skilled operator could interpret Morse code from the long and short periods of the dots and dashes. As a result the familiar single current Morse key and sounder came into use. This is the first data transmission system which is still in extensive use today on the amateur bands. Picture: Science Museum
To get away from the need for highly trained operators, Sir Charles Wheatstone invented the ABC system in 1840. It indicates the letter directly by a pointer, like a clock hand. There is a hand generator on the front, a dial with 30 keys round the edge and a pointer. The whole thing was known as a communicator. A separate receiver also had a single pointer.
To work it one pressed the key for the letter wanted and wound the generator. The pointer would go round until it reached the key pressed and then it disconnected the generator. Pressing another key then allowed the pointer to rotate to the next letter and so on.
The generator sent alternating half cycles of current to the line and the receiving pointer moved round a letter at a time, like a stepper motor, till it reached the letter being sent.
It was pretty simple, robust, and needed little skill to operate. Speeds were up to about 15 words per minute.
These articles copyright 1987, AG Hobbs & SM Hallas.