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It was difficult under such circumstances to steer a straight course, and sailing-ships possessed no power of being readily stopped when a fault or accident occurred. Attempts to lay cables from sailing-ships towed by steamers was another source of failure. Mr. Newall, in his evidence, said that the hemp-covered cable which he attempted to lay in 1859, between Candia and Egypt, had the hemp eaten off by the teredo in a very short time, and it was too weak to recover for repairing. The first cable ever manufactured with due regard to the principle of careful supervision, testing under water, and being retained quietly in that condition until it was laid, was the Malta and Alexandria cable, laid in 1861. This cable was submerged in too shallow water, for many miles in less depth than 20 fathoms; the result was the frequent recurrence of fracture from being rolled about by the surf, and yet this cable was only finally abandoned last year; not because it could not be kept in repair, but because it was too expensive to keep in order. There are difficulties and disasters peculiar to every attempt, and the grand result is that, one way or another, they were overcome, or else they suggested such modifications that their recurrence was avoided, and an accident to a well-manufactured cable no longer constitutes a loss.

Any of these conditions would nowadays be regarded as enough to condemn the most carefully-manufactured cable. Protection or Outer Sheath : In current time every cable have an outer sheath is used of protecting the cable. Shielding or Armor : It is the external protection of the conductor against the temperature, sun, rain etc. These are generally made of polymeric material. The insulation of a telephone cable is composed of dry cellulose (in the form of paper tape wrapped around the conductor or paper pulp applied to the conductor) or of polyethylene. Twisted Pairs Cables :- In this cable the two cables are twisted together and are color coded. The Red Sea and Indian cables are said to have been imperfectly manufactured and laid too taut, but they were not tested under water from the time of manufacture until they were placed at the bottom of the sea, and this one grand omission, largely due to inexperience, is enough, without the recriminatory points, to condemn to loss and failure any cable whatever.

The defendant put up the banner, at first suspending it by a rope, but the rope breaking, substituted for it a wire cable of the defendant's, and, the plaintiff says, did so without further orders. Armstrong’s first important invention was the regenerative circuit he developed in 1912 (see photo above right). It hardly is denied that there was evidence of negligence, but it ws held by the Circuit Court of Appeals that the defendant's relation to the work ceased when the banner was hung, that it had no further control over it and was not liable for what happened thereafter. One experienced gentleman in his evidence said these cables were "such as nobody should have laid in deep water." It is sufficient at present to know that they have failed from neglect or inexperience, and that they, among other failures, have established the principles which have since insured success. These cables have a core called cladding which is optically rarer than the core. The core can be made of copper, nickel-plated copper or nickel (white metal).

U: copper core; U and R indicate rigid cores, K a flexible core. Cables have been recovered from depths of 1,200 fathoms with all the hemp eaten away, and the core pitted with these marine animals. Lightning is still another source of injury to cables; this is, however, so readily guarded against that we no longer hear of injury from this cause: it is said to have destroyed three cables. These minute defects must, however, kill the cable in more or less time, and the principle is established that every inch should be tested in course of manufacture, and rejected if there is any irregularity of condition to cause suspicion. These are applied to isolate the signals that pass through the inner side of the cable and prevent it from external interference. These have very less probability of interference. We use shielded cables used when there is some unwanted electrical noise or some electromagnetic interference that the transmission of power. Overall the electrical cables are important for efficiently transportation of electrical power in every sectors.

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