Telegraph line
As a telegraph line is called fixed wired connections for telegraphy .
For the construction of the above-ground telegraph lines, impregnated poles 7-10 meters long and 12-15 cm thick, to which the porcelain insulation devices are screwed onto iron supports, are used. At the end of the 19th century, the German Reich Telegraph Administration used the double bell specified by Chauvin on a hook-shaped screw support.
Galvanized iron wire with a diameter of 2.5–5 mm is generally used to manufacture the cables; Occasionally bronze is also used. The underground lines are made of copper wires or copper braids insulated with gutta-percha ; Usually 4 or 7 such cores are stranded to form a cable and covered with a protective sheath of galvanized iron wires.
For crossing bodies of water, the cables are given a second protective sheath made of thicker wires and they are also enclosed in galvanized cast iron articulated sleeves. Underground lines are less susceptible to damage, but require excellent insulation and significant installation costs, while their usability over longer distances is restricted to a certain extent by the charge phenomena adhering to the cables ( capacitance ).
Already used when electrical telegraphy came into being, it has only become more widespread since 1876, after the German Reich Telegraph Administration had pioneered the creation of its extensive underground line network. In 1886 Germany owned 5,648 km, France 1,661 km, Great Britain 1,146 km and Russia 289 km underground lines.
The submarine connections developed much faster and more powerfully. The large submarine cables are constructed in a similar way to the land cables, but contain only one conductor because of the inevitable induction . In 1851 the first usable submarine cable was laid between Dover and Calais , and in 1866 the first cable connection between Europe and America was established.
In 1886 12 cables were used for telegraphic traffic in both parts of the world: 8 of them go from Great Britain and Ireland , 2 from France to North America ; 2 cables from Portugal to South America .
In 1887, the total length of existing submarine cables was 113,565 nautical miles, including 103,396 nautical miles owned by private companies and only 10,169 under state administration.
