The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . ing the battery to line. On circuits where the trafficis Small it is usual to make one wire serve several stations. Theconnexions at an intermediate orwayside station are shown at is a switch, consisting of three blocks of brass fixed to an insulat-ing base. W may be made the terminal station of L, by insertingplug 3, and of L., by inserting plug 2, or the instruments may b
The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . ing the battery to line. On circuits where the trafficis Small it is usual to make one wire serve several stations. Theconnexions at an intermediate orwayside station are shown at is a switch, consisting of three blocks of brass fixed to an insulat-ing base. W may be made the terminal station of L, by insertingplug 3, and of L., by inserting plug 2, or the instruments may becut out of circuit by inserting plug 1. In ordinary circumstancesthe messages from all stations ard sent through the whole line, andthus the operator at any station may transmit, if the line is free,by manipulating his key. The greatest inconvenience of this systemarises from the varying strength and resistance of the batteriesused at the different stations. As, however, delicate recordinginstruments are seldom required on such circuits little difficulty isexperienced. (2) The connexions for positive and negative current or single-- needle working on open circuit are shown in fig. 21, in which all thelettersthe. Doublecurrent. is a reversingkey. The levers 1 and 2 H^ rt) * rt-\ jiress against L— Fig- 21. I—I I I the stops a wlien the line is free ; hence the line is to earth at bothends. But, if lever 1 is depressed, one pole of the battery is put,0 line ; if 2 is depressed, the other pole is put to thoIine. Inthis way the needles of tlie receiving instrument may bo made toturn to either left or riglit; and, if we call a motion to the left adot and a motion to the ri»ht a dash, the Morse alphabet may beread from these motions, The connexions for wayside stations areillustrated at W, and will be readily understood from the descrip-tion given under single-current working above. (3) When the line consists in whole or in part of undergroundor submarine cable tlie capacity cau
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