. The telephone system of the British post office. A practical handbook . e through the right hand coil to the topright hand terminal. The terminal which joins the two coils together is Polarised Indicator Relay. 65 only used for trunk working, and we may therefore leave it out of con-sideration for the present. The armature is normally held upon the righthand contact point by means of the spiral spring, the tension upon whichcan be varied at will by turning the screw which works upon the movablering carrying the hook. The left hand contact point, which is insulated,is connected to the fourth
. The telephone system of the British post office. A practical handbook . e through the right hand coil to the topright hand terminal. The terminal which joins the two coils together is Polarised Indicator Relay. 65 only used for trunk working, and we may therefore leave it out of con-sideration for the present. The armature is normally held upon the righthand contact point by means of the spiral spring, the tension upon whichcan be varied at will by turning the screw which works upon the movablering carrying the hook. The left hand contact point, which is insulated,is connected to the fourth terminal, and the body of the instrument towhich the armature is attached forms the other terminal. The connec-tions are made by brass screws, which not only hold the instrument inposition, but at the same time fit into pieces of brass which are, behindthe switch, connected to the various points. A current passing throughthe indicator from left to right makes the left hand electro-magnet into asouth pole, and tbe right into a north pole, thus deflecting the iron needle. which by induction is made north, to the left. At the same time thearmature is deflected on to the left hand contact point. Both ends ofthe armature are made into south poles by induction from the lowermagnet; thus the right hand side is attracted and the left hand side isrepelled, so closing the local circuit. The use of this local circuit is toclose the circuit of an electric bell, thus calling attention to the instruments are mounted upon a copper strip, thus connecting oneside of all the local circuits together. When two subscribers are put through, their permanent currents arestopped by the removal of their receivers, and they speak through in theordinary way, the needles thus banging vertically and indicating that these F 66 Peymanent Current Working. subscribers are engaged. Immediately they put their receivers back uponthe rests as in Figure 55 (3 and 4) their permanent currents flow on to th
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
