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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1876 edition. Excerpt: ...subject to accidents of various kinds, most of which produce variable resistance. But subterranean and submarine wires are free from most of these vicissitudes. The resistance of their insulating coating is practically constant. Cables lie beneath the sea upon a cushion of equable temperature, and they are far removed from atmospheric disturbances, though they are still 150 Rheostats. liable to the effects of earth's currents, and probably to those of atmospheric electricity. 164. Now what effect has this variation of the resistance of the line wire upon duplex working, and how is it provided for? Clearly it disturbs the equality of the line and compensating currents, and causes the one to preponderate over the other; and if no means were adopted to compensate for this variation, duplex telegraphy would be impossible. Therefore the compensation circuit is not only made similar to the line circuit in resistance at the outset, but it is supplied with an apparatus called the rheostat, which enables this resistance to be varied with the variation of the line circuit 165. The rheostat, fig. 100, is a box of resistance coils so arranged that the motion of the handles adjusts the resistance of the compensation circuit at will. The figures over which these move indicate the number of units of resistance which will be inserted in the circuit according to the position of the handles. The arrangement is such that each handle can move over only one half of the dial: thus the maximum resistance which could be inserted in the circuit by the rheostat shown in fig. 100 would be 4400." But as an adjunct to this a coil offering a resistance of 4000" is placed at the side of the main box, and this can be cut out of the circuit or inserted in it at will by...
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Product details

  • Paperback | 78 pages
  • 189 x 246 x 4mm | 154g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236529928
  • 9781236529923