. The telephone system of the British post office. A practical handbook . speaking circuits. In one position No. i set, together with all itstaps, is connected to the signalling fuse tablet in the test room, and in thesecond position No. 2 set is similarly connected. The charging switchinsulates or charges the set of cells not in use. It is, of course, needless tosay that all leads to the points of distribution, viz., to the fuse tablets, areof heavy wire, usually seven-sixteens stranded copper insulated withvulcanised rubber. Fuses are inserted in all the leads from the cellsbefore they pass
. The telephone system of the British post office. A practical handbook . speaking circuits. In one position No. i set, together with all itstaps, is connected to the signalling fuse tablet in the test room, and in thesecond position No. 2 set is similarly connected. The charging switchinsulates or charges the set of cells not in use. It is, of course, needless tosay that all leads to the points of distribution, viz., to the fuse tablets, areof heavy wire, usually seven-sixteens stranded copper insulated withvulcanised rubber. Fuses are inserted in all the leads from the cellsbefore they pass to the charging and controlling switches. In the case ofthe signalling leads the slight resistance inserted is not of such vital con-sequence. A fault at a switch section blows the small fuse on the fusetablet, but a fault between the fuse tablet and the cells blows the fuse inthe leads of the cells affected. It has been found possible to considerably reduce the number of primarybatteries in use at the various exchanges by suitably grouping the various set! rlijMitilj. Figure 127. circuits on to a single set of batteries. The whole of the permanentcurrents are arranged precisely as described in the case of accumulatorworking, but as no fuse tablet is necessary the batteries are grouped uponthe battery tablet as shewn in Figure 127. Two sets of batteries are used,one being a stand-by in case of failure. The left central holes upon thefirst row of test holes are used for the leads from the sections. The topholes are the leads from set i, and the bottom ones from set 2, so that itwill be seen that, by reversing the U links from the top holes to thebottom ones, set No. 2 will be joined up in place of set No. i (as shewn). The local and main permanent current tags are teed at the sections asalready indicated. Each section occupies two sets of test holes, so thatone battery tablet will accommodate the permanent current leads fortwelve sections. The trunk ringing, self restoring, and
Size: 2155px × 1159px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
