. The telephone system of the British post office. A practical handbook . he left hand side of thedivided lever, through the left hand bottom spring back to the will be seen that when the lever is depressed the primary circuit isbroken, thus preventing the battery from being run down. The secondarycircuit is from the upper switch-spring upon the switch board ^shown atthe side of the tablet) through the right hand side of the divided lever,through the right hand bottom spring, through the secondary of the inductioncoil to the top right hand spring, through the receiver back to the le
. The telephone system of the British post office. A practical handbook . he left hand side of thedivided lever, through the left hand bottom spring back to the will be seen that when the lever is depressed the primary circuit isbroken, thus preventing the battery from being run down. The secondarycircuit is from the upper switch-spring upon the switch board ^shown atthe side of the tablet) through the right hand side of the divided lever,through the right hand bottom spring, through the secondary of the inductioncoil to the top right hand spring, through the receiver back to the left 64 CovneciioftS, hand bottom spring (which we have seen also serves for one side of themicrophone) to the bottom spring of the switch-spring from which westarted. The button upon the telephone when depressed connects thebottom right switch-spring to the top right spring. The secondary of theinduction coil is thus short-circuited from the top right spring, throughthe bottom right spring, through the right side of the divided lever to theother end of the divided Figure 53. The connections are shown in skeleton (in Figure 53), and the variousparts of the apparatus labelled accordingly. It is usual to hang the telephone upon the lever when not in leaves the call battery always on to the operators peg, but cutsthe primary and secondary circuits. The fact that the operator is unable to listen to conversations might atfirst sight appear a great advantage, but in reality it is not so, as theoperator would not find out that the subscribers were not speaking if thepair of pegs and cords were defective, and this is a very common fault. A new switch has recently been designed for the larger offices, whichis not a secret one. The replacing of indicator shutters takes time, andthe tendency of all modern telephone engineers is to make everythingautomatic. Accordingly, in place of the indicator wife a shutter a polar-ised indicator relay is inserted. This instrument (Figure
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
