Telegraphy

This section is devoted to methods of comunication involving telegraphy. The telegraph is a system of communication employing electrical apparatus to transmit and receive signals in accordance with a code of electrical pulses. Originally the term telegraphy referred to any form of communication over long distances in which messages were transmitted by signs or sounds.

The Murray Optical Telegraph consisted of six rectangular shutters or "ports", suspended within wooden frames. The opening or closing of these produced a combination of sixty three phrases and letters plus "at rest". The Optical Telegraph was commissioned by the British Admiralty in 1795 and specially equipped stations were built along the south coast of England, each manned by two 'glass men' who observed adjoining stations by telescope and two 'rope men' who operated the shutter ropes.

Pre-electric shutter and semaphore telegraphs remained in use until the introduction of the electric telegraph in 1839. Cooke and Wheatstone realised that an electric telegraph had the potential to control the chaotic movement of trains on the public railways which were starting to appear across the country. By 1839, they had perfected the diamond shaped Five-Needle Telegraph, which was installed on a 12 mile stretch of the Great Western Railway. Electric current caused two of the needles to move. The point of intersection on the grid indicated the letter being transmitted. The use of two needles meant that only 20 letters could be indicated - C,J,Q,U,X and Z were omitted - thus causing the operator to resort to phonetic spelling! This alphabetic telegraph was replaced by a faster 2-needle coded telegraph in 1844 - just about the time Samuel Morse was demonstrating his telegraph in the USA.

As the telegraph was originally developed for railway use, one had to visit the railway ticket office in order to send a telegram. The Telegraph Sounder alerted the booking clerk, who had to deal with the telegraph and sell tickets at the same time! On receiving the signal current from the distant Morse key, a coil pulls the iron bar against the stop, making a clicking sound, indicating a dash or dot.

The "Hedgehog" Transformer (see opposite), so called because of its appearance, was manufactured by the National Telephone Company on 31st March 1905. Like the later GPO 'B' Telegraph Relay, it was used to boost signals over long distances. Telegrams were originally transmitted by this method. Modern transformers now use flat steel laminations for the core, but hedgehog transformers were around for quite a while before being completely superseded.