. The telephone system of the British post office. A practical handbook . two-and-a-half cross-connection strips. The remaining twelve tagsare in use for the one negative and the ten positive leads coming from theten A circuits. These ten tags are, of course, all teed together. The speaking batteries are to be found upon the last set of tags uponthe central bottom cross-connection strip. Actual Connections. 113 The tags which are left disconnected will readily be seen from a verybrief consideration of Figure 96. The speaking circuits are similarlyarranged and marked. The call wire occupies the
. The telephone system of the British post office. A practical handbook . two-and-a-half cross-connection strips. The remaining twelve tagsare in use for the one negative and the ten positive leads coming from theten A circuits. These ten tags are, of course, all teed together. The speaking batteries are to be found upon the last set of tags uponthe central bottom cross-connection strip. Actual Connections. 113 The tags which are left disconnected will readily be seen from a verybrief consideration of Figure 96. The speaking circuits are similarlyarranged and marked. The call wire occupies the same relative positionas the first two A circuit positive lead tags. Thus it will be seen how easyit is to trace the tags corresponding to any particular circuit. A single battery must be used to work the whole exchange, but the bat-tery leads to each section should pass through U links upon the test board,so that a short-circuit upon one of the switch-springs may be readilylocalised. Where secondary cells are in use, the leads pass through fuses, ■^ StfW^aiy d^Tfr. Figure 98. which are blown in the event of a fault. This fuse indicates upon whatsection or transfer board the fault lies. In the case of transfer boards theA and B circuits are frequently divided into groups, so that the position ofthe fault may the more readily be ascertained. The top spring is con-nected to the positive and the bottom spring to the negative pole of thebattery, so that if the top spring touches the central spring in the normalcondition the battery is short-circuited. Upon a switch section this faultblows the sections fuse. The fuse is then replaced by a glow lampand a peg inserted into each switch-spring in turn until the fault disappears, t 114 Faults and their Localisation. due to the contact being broken with the bottom spring. A short-circuit,which occurs immediately the peg is inserted, due to a faulty bottom spring,may similarly be As a rule, this is instantly discovered by theop
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
