Submarine communications cable

“ Countries far apart, and isolated by oceans, have, by means of deep-sea cables, been brought into intimate relation, and made sharers of one another’s intelligence, enterprise, and civilizing instincts. What the overland telegraph has done toward bringing local states and communities into contact, the submarine cable has done for the remote nations.
In form, an ocean cable differs much from the simple wire which constitutes the conductor of an overland or even underground telegraph. ”

“ According to recent statistics, the North Atlantic Ocean is now crossed by no less than 17 cables, the number of cables all over the world being 2937, with a total length of 291,137 nautical miles.
Before describing the actual working of a submarine cable, a few words on cable-laying may be of interest. Before the cable-ship starts, another vessel is sent over the proposed course to make soundings. Galvanized steel pianoforte wire is used for sounding, and it is wound in lengths of 3 or 4 nautical miles on gun-metal drums. ”

“ Its use in a submarine cable is to confine the electric current to the conductor or wire, so that it travels along it from one station to the other without escaping to the water, and through that to the earth (which, as we have already said, is the neighbouring conductor, and the return part of the circuit) on its way. It is therefore of course important that there shall be no flaw in the insulator, and in order to protect it from strain and violence, it is covered with a strong guard or sheathing. ”

“ Before laying a submarine cable between the proposed places it is extremely important to take soundings and otherwise survey the ocean, so as to determine the exact route the cable should take. A cable is too costly to be flung away anywhere on the sea-bottom, and the sea-bottom is sometimes of a very unfavourable character. ”

“ The engineers were fast learning the rigorous conditions of submarine telegraphy; in its essentials the Dover-Calais line continues to be the type of deep-sea cables to-day. The success of the wire laid across the British Channel incited other ventures of the kind. Many of them, through careless construction or unskilful laying, were utter failures. At last, in 1855, a submarine line 171 miles in length gave excellent service, as it united Varna with Constantinople; this was the greatest length of satisfactory cable until the submergence of an Atlantic line. ”

“ Communication by wireless cannot be interrupted by a belligerent. With a submarine cable it is otherwise. The possibility of cutting the cable exists, and if a belligerent possesses naval superiority the cable is cut, as was the German cable near the Azores by one of Germany's enemies, and as was the British cable near Fanning Island by a German naval force. Since a cable is subject to hostile attack, the responsibility falls upon the belligerent, and not upon the neutral, to prevent cable communication. ”

“ In all there are more than 150,000 miles of submarine cable under the waters of the globe, and there is a fleet of forty ships, large and small, fitted out solely for the purpose of laying and repairing submarine cables. Nowadays the laying of an Atlantic cable attracts no attention, and the fishing up of a slender rope less than an inch thick from the floor of the ocean, 12,000 or 15,000 feet down, is a thing done a dozen times a year. ”

“ It was in 1851 that an electric cable was actually laid in the open sea, and worked successfully; and the wire which then connected Dover with Calais was beyond question the first important line of submarine telegraph ever attempted. In the year 1850, Mr. Brett obtained a concession from the French Government for effecting this object,—an object regarded at the time as one purely chimerical, and decried by the press as a gigantic swindle. The cable which was made for the purpose consisted of a solid copper wire, covered with gutta percha. ”

“ There are two forces, in fact, pulling against each other through the gutta-percha as a neutral medium,—that is, the electricity in the wire, and the opposite electricity in the film of water immediately surrounding the cable; and to that extent the power of the current in the enclosed wire is weakened. A submarine cable, when in the water, is virtually a lengthened-out Leyden jar; it transmits signals while being charged and discharged, instead of merely allowing a stream to flow evenly along it: it is a bottle for holding electricity rather than a pipe for carrying it ”

“ The practical working of a submarine cable differs in many respects from that of a land telegraph line. The currents used in submarine telegraphy are extremely small, contrary to the popular impression. An insulated cable acts like a Leyden jar, in the sense that it accumulates electricity and does not quickly part with it, as does a bare overhead wire. In the case of a very long cable, such as one across the Atlantic, a current continues to flow from it for some time after the battery is disconnected. ”

“ In 1903 an American cable was laid to the Philippines from San Francisco by way of Hawaii. Thus, by means of the overland telegraph and the submarine cable, it is now possible to transmit a message in a few hours to almost any country on the globe.
Submarine Cables are laid on the bottom of the sea. They require not only good insulation, but great tensile strength, else they will not support their own weights when lowered from the vessel to the bottom of the sea. This tensile strength is acquired by wrapping the guttapercha insulation with a sheathing of steel wire. ”

“ The receiving instruments for working a submarine cable are different from those used in working land-lines. Inasmuch as the current travels full strength, like a bullet, through a land-line, and in the form of an undulation or wave through a cable, so is it necessary to have different kinds of receiving instruments for each. In a land-line powerful currents can be used with impunity, and these can be made, by means of electro-magnetism, to move comparatively heavy pieces of mechanism in giving signals. ”

“ Wires, or stays, as they are called, fore and aft are used to brace and hold the periscope and signal stanchion firm against the force of the water which presses on them when the craft is submerged and under way. The tops of the signal stanchion and the periscope are also braced by a signal halyard, which is simply a wire, or cable, stretched taut between them.
On all modern submarines a wireless aerial is attached to a mast which can be folded down flat on the deck when the submarine is getting ready to make a dive. ”

“ The Atlantic telegraph, it is said by some, was a failure. Well, if it were so, replies Mr. Field, I should say (as is said of many a man, that he did more by his death than by his life) that even in its failure it has been of immense benefit to the science of the world, for it has been the great experimenting cable. No electrician ever had so long a line to work upon before; and hence the science of submarine telegraphy never made such rapid progress as after that great experiment. ”

“ Moreover, they were here supported technically by the views of the responsible electrician, as well as by such high authorities as Michael Faraday and Morse. The latter reported that “large coated wires used beneath the water or the earth are worse conductors—so far as velocity of transmission is concerned—than small ones; and, therefore, are not so well suited as small ones for the purposes of submarine transmission of telegraphic signals.” Faraday had stated: “The larger the wire, the more electricity was required to charge it ”

“ Telephone system:
general assessment: adequate, modern networks reach all areas; good mobile telephone and international service domestic: microwave radio relay trunk system; extensive open-wire connections; submarine cable to offshore islands international: country code - 30; landing point for the SEA-ME-WE-3 optical telecommunications submarine cable that provides links to Europe, Middle East, and Asia; a number of smaller submarine cables provide connectivity to various parts of Europe, the Middle East, and Cyprus ”

“ In reply to your inquiries, we beg to state that we should not be willing to manufacture and lay a Submarine Telegraph Cable across the Atlantic, from Ireland to Newfoundland, assuming the entire risk, as we consider that would be too great a responsibility for any single firm to undertake; but we are so confident that these points can be connected by a good and durable cable, that we are willing to contract to do the work, and stake a large sum upon its successful laying and working. ”

“ In the French Atlantic cable no current can be detected by the most delicate galvanoscope at America for the first tenth of a second after it has been put on at Brest; and it takes about half a second for the received current to reach its maximum value. This is owing to the phenomenon of induction, very important in submarine cables, but almost entirely absent in land lines. In submarine cables, as is well known, the copper wire which conveys the current is insulated from the sea-water by an envelope, usually of gutta-percha. ”

“ In addition to the above, there have been laid across American rivers, since 1854, 95 lines, in lengths of from 120 feet to two miles, and comprising from 120 feet to 6 miles of insulated wire each,—making an aggregate of 250 miles of subaqueous wire in operation on this continent, and a total of 6,979 miles of cable, and 11,127 miles of submarine wire in operation in all parts of the world. ”

“ It has been found that the electrostatic capacity of one mile of submarine cable is equal to the capacity of 20 miles of overhead line, and as the effect of capacity is to retard the current and reduce the speed of working, it is evident that where there is any great length of cable in the circuit the distance of possible transmission is enormously reduced. ”

“ The High Contracting Parties agree to insist, as far as possible, when they shall authorize the landing of a submarine cable, upon suitable conditions of safety, both as regards the track of the cable and its dimensions. ”

“ No insulation of a submarine cable is ever so perfect as to withstand the influence of these electrical phenomena, which correspond [Pg 286] in some particulars to storms in the ordinary atmosphere, their direction generally being from east to west. Their action is immediately communicated to all conductors of electricity, and a struggle set up between the natural current and that used artificially in sending messages. ”

“ This deep-sea sounding is a very necessary feature of cable laying, as unexpected depths of water or unlooked for changes in submarine geography, when not taken into account, might prove disastrous to the cable being laid. The sounding apparatus is of great interest, being a compact little affair consisting of a small engine that with a self-acting brake helps regulate the wire sounding-line as it is lowered into the water, and after sounding heaves it up again. ”

“ Submarine cables have multiplied recently, and almost every ocean flows over the mysterious wires which flash intelligence beneath the rolling waters from point to point of the civilized world. By a telegraph-cable, which is partly submarine, the India Office in Westminster is united with the Governor-General and his Council at Calcutta. ”

“ If it becomes absolutely necessary to reverse the propellers when paying out cable, men paying it out must haul it in taut and keep it above the wheel and clear of it. The planting vessel should not pass nearer than 25 feet to the distribution box boat when cable is leading out from the latter, nor should it pass over any cable, if it can be avoided, if the depth is less than 16 feet. ”

“ ELECTRICAL GRAPNEL FOR SUBMARINE CABLES AND TORPEDO LINES. By H. KINGSFORD.
All those who are acquainted with the cable-lifting branch of submarine telegraphy are well aware how important a matter it is in grappling to be certain of the instant the cable is hooked. This importance increases, of course, with the age and consequent weakness of the material, as the injury caused by dragging a cable along the bottom is obviously very great. ”

“ We have many reasons to confirm the belief that a submarine cable, manufactured and laid with strict attention to all known principles, may be regarded as a substantial property, likely to last for any length of time; for there is no evidence whatever upon record which shows any decay of the insulating medium or copper conductor of a well-manufactured cable, i. e., there is no decay inherent in the nature of a cable; all deterioration is external ”

“ The weight per nautical mile of dielectric is the same in both cables, but each copper conductor of the former weighs 300 lb. per mile as compared with 160 lb. per mile in the latter. The transmission efficiency of the cables is practically equal, but the continuously loaded cable provides an additional circuit by superposing. Experiments conducted on this cable in 1914 proved the possibility of obtaining four circuits from a continuously loaded 4-wire submarine cable by introducing an improved method of balancing the electrostatic capacity of the conductors. ”

“ Reports have been published that German submarines have been fitted up with a wire and cable cutting appliance which would make it possible for them to break through nets at will, supposing, of course, that they had been caught by the nets in such a way that no vital parts of the underwater craft had been seriously damaged. A sketch of this wire cutting device was made by the captain of a merchantman, who, while in a small boat after his ship had been torpedoed, had come close enough to the attacking submarine to make the necessary observations. ”