Signalling

Watson Great Orme 1856

Great Ormes Head Station 1841

One of the earliest mechanical signalling devices used in Britain was the semaphore telegraph which was first established between London, Portsmouth (Naval) and Newmarket in 1774. Then in 1826 another semaphore telegraph was erected on hills between Holyhead and Liverpool, this comprised a 70 mile chain of eleven signalling stations placed within 7 miles of each other. A signal could be sent from one end to the other and back again in just over twenty-three seconds. Various other forms of semaphore were soon being developed in Europe and Russia, but where semaphore failed was in adverse weather conditions (fog, mists and storms) and of course at night – rendered this form of communication useless.

Voltaic Cell

Voltaic Cell

In the late eighteenth century, unsuccessful attempts at producing electrical machines for signalling were also made but it wasn’t until 1790s and the production of a continuous source of electric current (the Voltaic cell). As well as Oersted’s discovery in 1819 that a magnetised needle was deflected by an electric current flowing through a wire placed near the needle, that the possibilities of developing a successful signalling system was realised. Oersted’s discovery laid the foundation of the wired telegraph and soon several scientists (Pavel Schilling and Carl August von Steinheil amongst them) were endeavouring to perfect a communications system in which the movement of a magnetised needle could be used to indicate transmitted messages.

Five Needle Telegraph Patent (King's College Collection)

Five Needle Telegraph Patent (King’s College Collection)

In 1837 in England, the British physicist Charles Wheatstone in association with William Fothergill Cooke, took out a patent ‘for improvements in giving signals and sounding alarms in distant places by means of electric currents transmitted through metallic circuits.’ By changing the direction of the current, five pivotal needles could be made to move, two at a time, either to the left or the right and point towards a letter of the alphabet marked on the dial of the instrument. It was first fully adopted in 1839 by the Great Western Railway when it was used to connect the stations at Paddington and West Drayton.

In America, in the year that Wheatstone’s needle telegraph was patented in England, Samuel Morse with his partner Alfred Vail produced an experimental system of electric telegraphy which used an automatic printer to record incoming messages on a continuous roll of paper tape. To enable this to have a more practical use he invented a code, the Morse Code, tapped out by a Morse key. The received Morse symbols (dots and dashes) were at first embossed on the tape by a steel needle, but in a later development ink was used to print them and the printer became known as the Morse Inker. Alternatively in place of the inker or in conjunction with it, a Morse Sounder was used which was either a bell producing a ring or an instrument producing a click every time a dot or a dash was received. Morse also invented the relay which reinforced feeble signals at the receiving end by means of a current produced by a local battery. Although the results of this system were satisfactory, it was not until 1842 that Morse won support from the American Government and established the usefulness of his invention. Congress then advanced money for the setting up of a telegraph system between Baltimore and Washington and a year later the service began.

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