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History of telegraphy in Australia
Australia was a relatively early adopter of telegraph technology in the middle nineteenth century, despite its low population densities and the difficult conditions sometimes encountered in laying lines. From 1858 onwards, the major capitals were progressively linked, culminating in the addition of Perth in 1877. Australia was linked to the rest of the world for the first time in 1872, through the Overland Telegraph which ran some 3200 km from Adelaide through to Darwin. The network continued to expand in size and sophistication until 1959 and in heavy usage until 1945, after which time telephone usage began to erode public patronage of telegraphy services. The final publicly provided telegraphy service was closed in 1993.
==Basic description of a telegraph==
A telegraph is a device for transmitting and receiving messages over long distances, i.e., for telegraphy. An electrical telegraph uses electric current and magnetism to convert the manual typing of codes that represent words, into electrical impulses. These impulses are transmitted over a metallic circuit (overhead wires or underground cables) to a distant location. At the distant location the impulses are converted into magnetic fields that operate a mechanical device to make a sound or to move a visual indicator. The operator at the receiving end converts these sounds or signals into a written message. The code system used throughout Australia was the Morse Code.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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