Contains the full lesson along with a supporting toolkit, including teachers’ notes.
In 1804 Campillo (in Spain) devised a system with about 35 wires (one for each letter etc.) connected to a set of tubes of dilute acid at the receiving end. When the sender connected a battery to the wires at one end, bubbles appeared in the corresponding tube at the other end. An improved version was made by von Sömmering in 1809 which operated over a distance of a few kilometres. However, these electrochemical systems were complicated, slow and unreliable. In 1820 the potential of long distance electric communication improved greatly with the accidental discovery of the magnetic effect of electric current by Oerstedt. Over the following 25 years or so several electromagnetic communication systems were devised, generally using several wires. The first public telegraphy company in the world — the Electric Telegraph Company — was established in England In 1845. Meanwhile other systems were devised in the United States. Samuel Morse devised a coding system for the letters of the alphabet and numerals. Each letter was represented by a series of short and long pulses (usually called ‘dots’ and ‘dashes’). Morse’s system needed only one signal wire (along with a ground ‘wire’). An added advantage of his code was that messages could be sent at sea using lamps.
By 1851 Morse code was effectively the international standard telecommunications system and remained in widespread use for over 100 years. (In fact it was used as an international standard for maritime distress calls until 1999.)
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Its remit covers all kinds of transmission networks including: