. The practical telephone handbook and guide to the telephonic exchange . tes cemented to the sides of the tube, as shownin Fig. 192 at A. The resistance of the 24-volt lamps whencold is 520 ohms, and when incandescent and taking a currentof 0*11 ampere, is 240 ohms, the light then given beingabout one-third of a candle. Lamp-Jacks.—The lamps are held in position, and con-nection made to them by jacks of somewhat similar form toordinary spring - jacks,except that springs ofequal length are used, asshown at b in Fig. 192,which shows part of oneform of strip. When thelamps are in position, thesp
. The practical telephone handbook and guide to the telephonic exchange . tes cemented to the sides of the tube, as shownin Fig. 192 at A. The resistance of the 24-volt lamps whencold is 520 ohms, and when incandescent and taking a currentof 0*11 ampere, is 240 ohms, the light then given beingabout one-third of a candle. Lamp-Jacks.—The lamps are held in position, and con-nection made to them by jacks of somewhat similar form toordinary spring - jacks,except that springs ofequal length are used, asshown at b in Fig. 192,which shows part of oneform of strip. When thelamps are in position, thesprings bear on the brassplates of the lamps, andthe holes in the frontebonite strip throughwhich the lamps are in-serted are closed by lamp caps, which are small brass sockets,in the front of which opal plano-convex lenses are fitted, as d,Fig. 192. These caps protect the lamps from injury, andserve to spread the light, so that a signal can be plainly seenfrom any point at the front of the board. The opal caps areoften marked in such a manner as to inform the operator. Fig. 192.—Scale \ i68 PRACTICAL TELEPHONE HANDBOOK to what privileges the subscribers to which they belong areentitled. See Chapter XVII. The lamp-jacks are made up in strips to correspond in sizeand number of jacks to the spring-jack strips, as shown inFig. 193, which represents a strip of twenty as made by the
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
