The electric current : how produced and how used / by R. Mullineux Walmsley.

  • Walmsley, R. Mullineux (Robert Mullineux)
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: The electric current : how produced and how used / by R. Mullineux Walmsley. Source: Wellcome Collection.

    651/800 (page 635)
    Turning now for a moment to the general electrical plan of the board, the principle used is shown diagrammatically in Fig. 322. The whole switch-board is divided into sections, of which three, A, B and C, are shown in the figure, where, to avoid confusion, only the wires for six subscribers appear. Each subscriber has a switch spring similarly numbered on each section of the board. For instance, if the wire marked 401 on the left be traced, it will be found to run through a numbered pair of springs at each section, and to be finally put to earth after passing C. The line-wire of each subscriber therefore passes behind each section of the switch-board, and in each enters the appropriate switch-spring by the strip L (Fig. 320), and leaves it by the strip /. Each section is in charge of a separate attendant, but, though all the wires run to each section, the call apparatus for the various subscribers is divided between them. Thus, subscribers 1 to 200 have their call indicators, etc., fixed on section A, 201 to 400 on section B, and so on. As a matter of fact, each subscriber belonging to section A has two switch-springs on that section, one in its proper position amongst the springs of all the other subscribers on the board, and the other, known as his “ local,” in a separate part of the section. Attendant A can therefore only be “ rung-up ” by sub- scribers 1 to 200, but, having ascertained the wishes of the ringer-up, he can put him in communication with any other subscriber on the board by simply inserting the two pegs at the end of the same flexible conductor in the corresponding holes, thus bringing the line-wires of each into electrical connection through the strips L, the pegs, and the flexible conducting cord. Having explained the general plan of the board, we may now show the electrical position of the rest of the apparatus, and for this purpose are traced in Fig. 323 the connections of a line (No. 927) through four sections, D, E,