Cooke and Wheatstone telegraph
The receiver consisted of a number of needles that could be moved by electromagnetic coils to point to letters on a board.
This feature was liked by early users who were unwilling to learn codes, and employers who did not want to invest in staff training.
The change became more urgent as the insulation of some of the early installations deteriorated, causing some of the original wires to be unusable.
Once it was known that Tawell had boarded a train to London, the telegraph was used to signal ahead to the terminus at Paddington and have him arrested there.
Wheatstone, on the other hand, was an academic with no interest in commercial ventures, and he intended to publish his results and allow others to freely make use of them.
[1] This difference in outlook eventually led to a bitter dispute between the two men over claims to priority for the invention.
[2] Cooke had had some ideas for building a telegraph prior to his partnership with Wheatstone and had consulted scientist Michael Faraday for expert advice.
[3] In January 1837, Cooke proposed to the directors of the Liverpool and Manchester Railway a design for a 60-code mechanical telegraph.
Rope-haulage into main stations was common at this time to avoid noise and pollution, and in this case the gradient was too steep for the locomotive to ascend unaided.
[7] In May 1837 Cooke and Wheatstone patented a telegraph system that used a number of needles on a board that could be moved to point to letters of the alphabet.
A system was needed to signal to an engine house at Camden Town to start hauling the carriages back up the incline to the waiting locomotive.
[9] Cooke and Wheatstone had their first commercial success with a telegraph installed in 1838 on the Great Western Railway over the 13 miles (21 km) from Paddington station to West Drayton.
[11] As an interim measure, a two-needle system was used with three of the remaining working underground wires, which despite using only two needles had a greater number of codes.
Up to this point, the Great Western had insisted on exclusive use and refused Cooke permission to open public telegraph offices.
[19] The distance involved on the Blackwall Railway (four miles) was too far for steam signalling and the engineer, Robert Stephenson, strongly supported the electric solution.
[22] The one-needle telegraph proved highly successful on British railways, and 15,000 sets were still in use at the end of the nineteenth century.
[25] Murder suspect John Tawell was apprehended following the use of a needle telegraph message from Slough to Paddington on 1 January 1845.
The message was: A MURDER HAS GUST BEEN COMMITTED AT SALT HILL AND THE SUSPECTED MURDERER WAS SEEN TO TAKE A FIRST CLASS TICKET TO LONDON BY THE TRAIN WHICH LEFT SLOUGH AT 742 PM HE IS IN THE GARB OF A KWAKER WITH A GREAT COAT ON WHICH REACHES NEARLY DOWN TO HIS FEET HE IS IN THE LAST COMPARTMENT OF THE SECOND CLASS COMPARTMENT[26]The Cooke and Wheatstone system did not support punctuation, lower case, or some letters.
[26] The widely publicised arrest of Tawell was one of two events which brought the telegraph to greater public attention and led to its widespread use beyond railway signalling.
The first use of block working was probably in 1839 when George Stephenson had a Cooke and Wheatstone telegraph installed in the Clay Cross Tunnel of the North Midland Railway.
[29] The Cooke and Wheatstone telegraph consisted of a number of magnetic needles which could be made to turn a short distance either clockwise or anti-clockwise by electromagnetic induction from an energising winding.
[31] The five-needle telegraph with twenty possible needle positions was six codes short of being able to encode the complete alphabet.
[33] The economic need to reduce the number of wires in the end proved a stronger incentive than simplicity of use and led Cooke and Wheatstone to develop the two-needle and one-needle telegraphs.
Like the preceding two-needle system, the code units consisted of rapid deflections of the needle to either left or right in quick succession.
This was achieved through the provision of a sixth wire for common return making it possible to move just a single needle.
Many more codes are theoretically possible with common return signalling, but not all of them can conveniently be used with a grid indication display.
Two additional buttons were provided on the telegraph sets to enable the common return to be connected to either the positive or negative terminal of the battery according to the direction it was desired to move the needle.
