. The telephone system of the British post office. A practical handbook . ces of brass, so shaped thata brass plug may be inserted between them. When the plug is inserted,the drop indicator local contacts are joined up precisely as the self-restoring indicator locals. Thus when any local contact is made, thecircuit of the battery is made through either the day or the night bell, as■he case may be. The Telephone System of the Briiish Post Office. 93 CHAPTER XV. The B Switch Section. Where there are from three to five trunks, one B switch section is B section is of exactly the same size
. The telephone system of the British post office. A practical handbook . ces of brass, so shaped thata brass plug may be inserted between them. When the plug is inserted,the drop indicator local contacts are joined up precisely as the self-restoring indicator locals. Thus when any local contact is made, thecircuit of the battery is made through either the day or the night bell, as■he case may be. The Telephone System of the Briiish Post Office. 93 CHAPTER XV. The B Switch Section. Where there are from three to five trunks, one B switch section is B section is of exactly the same size and shape as the A sectionpreviously described ; but a strip of five five-point switch-springs is addedto accomodate the additional junctions. In addition to this six pairs ofcords, together with the necessary ringing and speaking keys, are certain cases two visual indicators are added; but this is a matterwhich will be dealt with later. A e- jft#j«4/«««v - Jan* r/an# •y^ftwvj* ^tttrep J»minma , ^ ^ma>r9 £••/»<•**« a^i^w^rrOM,. Figure 8o. The junctions all terminate upon five-point switch springs, and noindicators whatever are fitted upon them. The local contacts are preciselyas described in the case of the A section. The arrangement of theapparatus upon the switch is shown in Figure 80, and requires no further 94 function Clearing Arrangement. remark, save that the service wire to the Company terminates in one ofthe self-restoring indicators. In the event of anything going wrong may be used by leaving a peg in at either end, and thus leavingthe ring-off indicators in circuit. Upon a busy trunk switch section much time would be wasted incalling off each of the connections to the National. In order to avoid thisthe two inner contacts of the junction switch springs (Figure 8i) areconnected to an earthed battery, which, when the peg is withdrawn, sendsa current along both lines to the National, where it passes through anindicat
Size: 1575px × 1586px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
