History of the Atlantic Cable & Undersea Communications
Laying the Bass Strait Telephone
Laying the Bass Strait Telephone
THE development of electrical communication, particularly over long distances, has been of extraordinary rapidity in Australia during the last decade, and the last link in the chain of nation-wide telephone communication was welded recently by the laying of the submarine telephone cable between Victoria and Tasmania. A chain of high-grade telephone channels has now been established between all important centres, and it can be said that almost anyone in the Commonwealth can call up anyone else with comparative ease, while, by means of the overseas radio channels to Great Britain, New Zealand, and Java, contact has also been established with the majority of the countries of the world.
The development in telephone communication over the immense distances of Australia has been made possible largely by the use of what is known as the “carrier-current” system. Ordinary speech and music contain “frequencies” of the approximate range of from 20 to 20,000 cycles per second, but the transmission of frequencies from 200 to 3,000 cycles per second over the telephone system is adequate for intelligibility. In an ordinary telephone circuit, each frequency-component of the voice of the speaker is transmitted by an electrical current of the same frequency. In carrier-current operation the voice currents modulate high-frequency currents, which act as “carriers” for the message. By utilizing up to six different frequencies, and allocating one in each direction for a conversation, and by separating the various ranges of high-frequency currents by means of electrical filters and subsequently demodulating them (in short, by tuning as in wireless), it is possible to derive three telephone channels from a single pair of wires in addition to that obtained from the wires without any special treatment. This is the method adopted over long-distance land-lines in Australia.
By a development of this system, the unique new cable to Tasmania provides six telephone circuits, at least a dozen telegraph circuits, and a broadcasting circuit—all travelling through the one copper conductor wire! The concentric return conductor, corresponding to the second land-wire, consists of five copper tapes, which are insulated from the central copper conductor wire by a new substance known as “paragutta,” and covered again by a coating of the same material. This, the “business” portion of the cable, is no thicker than a small office ruler; with its packing and armouring, the whole completed cable is roughly some four inches in diameter.
Telegraphic communication between Tasmania and the mainland by means of a submarine cable has been in operation for many years, but telephone conversations are impossible over this, or any other, ordinary cable covering such a distance. It is the use of the newly-developed insulating material, “paragutta,” a composition of specially-treated rubber and gutta-percha, together with a quantity of wax, which enables a submarine cable of such a length to be utilized for telephone communication.
As a protection against the boring operations of the sea-worm known as the “teredo,” a copper tape is wound continuously round the cable—the activities of the teredo were the cause of the sheathing of wooden sailing ships with copper below water-level. This sea-worm’s appetite for insulating material is just as avid as it was for the timber of the old ships’ bottoms. The steel armouring for mechanical protection (abrasion against rocks and fouling with ships’ anchors are possible causes of damage) varies, depending upon the depth to which the cable is laid. The shore ends are armoured with sixteen steel wires, each about one-third of an inch in diameter, together with a further sixteen wires, each approximately one-fifth of an inch in diameter. Where the cable is in water of a depth of from five to twenty-five fathoms, the armouring consists of eleven wires, each a little over a quarter of an inch through, and the main portion of the cable, in a greater depth than twenty-five fathoms, is protected with sixteen one-fifth-inch wires.
THE routing of the cable was the subject of careful consideration, and it was finally decided that it should be laid from Apollo Bay in Victoria to Stanley in Tasmania, with Narracoopa, on King Island, as an intermediate point. This allowed the cable to be laid in two lengths, each of eighty nautical miles. From the transmission aspect it is desirable that the cable should be laid in two sections rather than in one complete length. Narracoopa is a very convenient half-way point at which to establish a repeater station; incidentally, the inhabitants of King Island are also able to obtain telephone communication with the mainland. The connecting land-lines that link Apollo Bay and Stanley with Melbourne and Launceston respectively consist of a single pair of copper wires. On the Victorian side a completely new pole-route has been made through the rugged forest country which lies between Birregurra and Forrest, while an existing route from Forrest to Apollo Bay has been specially treated and cleared of dangerous timber to reduce the possibility of interruption. Neat brick buildings to house the delicate land equipment, with houses alongside for the operating and maintenance staffs, have been erected at all the terminal points.
Messrs. Siemens Bros. and Co., of London, were given the contract for supplying and laying this cable, the contract price being £127,424/16/6, but additional costs in connection with the terminal bases and the repeater station at King Island will raise the total cost of the cable to £200,000.
To do the work, Messrs. Siemens Bros. sent out their 5,000-ton cable steamer Faraday (the largest cable ship in commission), with more than 160 nautical miles of cable, carefully coiled round truncated cones of cast-iron in four circular tanks beneath the hatches, where sea-water, just awash, covers the cable and keeps it in a supple state.
The cable, the first of its kind ever constructed by a British company, is the result of nine months’ exacting research work and calculations by expert cable engineers, under the supervision of Dr. A. Rosen, chief cable electrician for Siemens Bros., and Dr. Rosen came out on the Faraday to watch over the Bass Strait operations. The only other cable at all similar to this is one that was laid between Key West, in Florida, U.S.A., and the island of Cuba in 1930 by a German company, the length of the latter cable being 108 nautical miles. But it provides four telephone channels only.
The master of the Faraday (Captain Robert Allin) also acts as chief cable engineer, and on him and on Mr. R. Miller, the chief electrician, fell the chief responsibility of the work, which required exacting care and the study of intricate mathematical calculations—even if, as officers of the ship stated, the laying of the Bass Strait cable was mere “child’s play” compared to the laying of the 2,000-mile stretch of cable between Fanning Island and Fiji. This work was also carried out by the Faraday some years ago. The complement of the ship is 120 men, of whom twenty-six are officers, including electricians, doctor, and purser. There are seven special cable hands, including a storeman and a foreman, men who have received special training in handling the valuable cable.
THE first task of the Faraday was to buoy the route between Apollo Bay and King Island. An important factor in cable-laying is the discovery of a suitable sea-bed to take the line. In the case of the new Bass Strait cable, great assistance was rendered by Captain Evan Evans, master of the Taroona, who charted the sea-bed of the strait with the vessel’s echometer sounding device until a suitable route was discovered, and it was over this route that the Faraday laid a chain of six special buoys, each carrying an electric light, from Narracoopa to Apollo Bay.
The Faraday was then anchored about a mile out from the jetty to await favourable weather for the most difficult part of the work—the making of the shore connections. But really favourable weather never came, and the end of the cable was finally taken ashore through a heavy surf. Before a start was made with this rather complicated operation, the lengths of cable in the four tanks were linked together, a telephone circuit was formed, and the electricians spoke to each other through the whole 160 miles of cable. So far, so good; but elaborate tests are always carried out throughout the whole of the laying operations. In the meantime, buoys were hoisted on deck, and every preparation was made for the important job ahead.
The hull of the Faraday possesses what is called a “clipper bow” (I understand quite erroneously) —it is, at any rate, curved like that of an old-time clipper ship—and triple sheaves project still farther over the water. The stern is of the modern “cruiser” variety, and here again are triple sheaves. It is over these sheaves that the cable is finally paid out before it reaches the water, and they alone are sufficient to indicate that the ship was built especially for this business. The other little peculiarities in construction are not visible until one goes on board—the wide space left clear of any obstruction in the centre of the ship round the hatches, the circular shape of the latter, to say nothing of the laying-gears, the huge drums sunk below deck-level, and the mysteriously-figured dynamometer.
During laying operations great care is taken to prevent “kinking,” and the tension is continually tested by the dynamometers. Let us follow the cable from the time it leaves the tank. In laying a section from the forward tank, the cable was first passed through an “eye” attached to a cross-beam which runs across the centre of the tank, and then through a “knee” on the rim of the tank. Next it passes through wooden troughs to the laying gear, takes two or three turns round iron drums some eight feet in diameter, passes over a wheel set on the deck, under another wheel controlled by hydraulic pressure on the dynamometer (which records tension up to twenty-five tons), on again over another wheel, and so through the bow sheaves and out to the sea. In laying through the stern sheaves, the cable passes through an exactly similar set of contrivances, but the length of wooden troughing employed is greater. Strange as it may seem, laying from the bows has definite advantages over laying from the stern, where there is always the danger of the cable fouling the propeller. There is more space forward should it be necessary to effect repairs, and the weight of the cable bears it away so that only occasionally does it rub against the ship’s side.
In making the land connection a rope and a sheave are sent ashore and the line is brought back to the ship and passed through another sheave or round a drum. When this line is pulled by the deck-hands, the cable pays out. Three barrels are attached to the end of the cable when it reaches the water, another barrel is secured every twenty fathoms, and the cable-end is thus floated ashore. At Apollo Bay, owing to a heavy surf, the ship’s whale-boat was unable to reach the beach, and it finally became necessary to fire a rocket-line from the shore. This had to be recovered and attached to the rope before the cable-end could be hauled up to the trench that had been prepared for. it on the foreshore. From the trench the connections pass under the Ocean Road and so up to the brick building that houses the delicate land-equipment. The latter was also brought from England by the Faraday.
WHEN the land connections had been completed and tested, the Faraday slowly put out to sea, and, steaming along at between four and four and a half knots, commenced the actual laying of the cable. While the work was in progress, every hand was on duty. Meals were neglected, and the commander was on the bridge for fifteen consecutive hours. From Apollo Bay forty nautical miles of cable were laid “visually” along the buoyed route. An end was then attached to a special gigantic buoy, and the Faraday once more steamed back, picking up the smaller buoys that had marked this section of the route. Forty miles of cable had still to be laid to the midway buoy above-mentioned to complete the first section of the cable.
Next the Faraday went on to Narracoopa, on Sea Elephant Bay, King Island, to make the shore connections there, and once again the work had to be carried out under bad conditions—even more unfavourable than those at Apollo Bay. This is a dangerous coast; the weather was threatening; a heavy surf broke on the shore, and ran back hissing and foaming, only to be swallowed up as the next great wave came rolling in. The commander decided to risk the surf, and the cutter and dinghy were sent away from the ship laden with the delicate land-equipment, and the hauling ropes with which to drag the cable to the repeater station. The dinghy was overturned in the surf, but the three occupants reached the shore in safety, the assistant purser, who was in the boat, showing great presence of mind, and taking with him the radio transmitter, which is used by the shore-party to keep in touch with the ship.
In a race against time, electricians and cable-engineers worked without sleep for thirty-six hours, setting up the shore equipment and making the necessary preparations for landing the cable-end. It was essential that the work should be completed before the tide turned, and this meant carrying on after nightfall, when all was ready. A bright moon lit up the scene, searchlights from the ship showed up hurrying figures and played on the restless surf, while huge bonfires ashore threw a red and wavering glow on the beach. Residents of King Island crowded round, thrilled at the spectacular scene. Amid great excitement, the shore-end was landed at 3 a.m., and connections were made, just as the tide was turning.
The Faraday immediately began to pay out the cable, turning wheels and straining cable being illuminated by a battery of flood-lights on the after-deck. The buoyed end of the cable was reached soon after midnight, and the ship’s “jointer” finished the intricate task of splicing the two ends just before dawn. The completed cable giving telephonic communication between King Island and the mainland was dropped overboard at 5.30 a.m. Tests of the cable were made, and the results were perfect. The splicing is, of course, highly skilled work, and the expert “jointer” who does this job is probably the fittest man on the ship, being constantly under the observation of the doctor. His hands are continually tested for acids—any trace of these would damage the delicate copper conductor wire, which is the very life of the cable.
From King Island to Stanley the work was carried out on exactly similar lines, bow and stern sheaves being used alternately. Further delay was caused by heavy weather, and the Faraday had been exactly four weeks in Bass Strait when the final splice of the two ends was completed one night, midway between Stanley and King Island. “With the release of the cable, following this final splicing, a ceremony in perpetuation of an old custom in cable-ships was held—the burial at sea of an effigy of a sailor. When all was ready to release the cable, a procession of pall-bearers appeared on deck, amidst them, on a stretcher, the ‘sailor’—named after the toughest seaman on the ship. A sea chanty was sung, a solemn requiem intoned, a brief service conducted, and the ‘sailor’ was lashed to the cable. Then a rope holding the cable was severed with an axe, and cable and ‘sailor’ disappeared together in the depths of the sea.” Although the Faraday can lay as much as 200 miles in the day, she usually steams along at from six to eight knots while paying out a cable, or in a heavy swell the pace may be very much slower.
While the cable is being paid out, it is connected with a set of instruments in a special cable-control room, where every inch is tested by the electricians, and where every detail is recorded by the instruments. One officer is in constant telephonic communication with the shore, using a special long-distance transmitter and receiver recently designed by Siemens Bros. The chief electrician watches continually a spot of reflected light on a long glass scale—any irregularity in the behaviour of this spot indicates a fault in the cable. A fault in the insulation is detected by one instrument, a fault in the conductor by another, and each of these instruments is in the charge of an assistant electrician, who never leaves his post as long as the cable is being paid out. Not only do these instruments infallibly detect any fault, but they also indicate its exact distance from the ship. If the fault is only three or four miles away, the cable will probably be wound in again and immediate repairs effected. Tests of the temperature of the water immediately above the sea-floor are also continually taken with maximum and minimum thermometers, which are lowered over the ship’s side in copper casings. The temperatures have an important bearing on the tests conducted in the cable-control room. Power for conducting all the intricate electric tests comes from rows and rows of accumulators which fill the shelves covering the four walls of an adjoining room from end to end.
The Faraday has laid thousands of miles of cable, but the greater part of her time is spent in repairing deep-sea cables in all parts of the world. The senior officers and a number of the men before the mast have had a great many years’ experience in their special duties. Captain Allin has served in cable-ships for 36 years, and has been in the Faraday since 1924, the year in which the ship was built. The vessel, which, by the way, is fitted up quite as comfortably, if not so ornately, as the latest passenger liner, has a steaming range of 11,000 miles and a speed of 11 knots.
Copyright © 2008 FTL Design
Last revised: 9 July, 2010
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