. The telephone system of the British post office. A practical handbook . Figure 63. curved end of the shorter spring, and the long spring rests upon the backpart of the brass peg. This raises the two outer springs off the innersprings, thus leaving the inner springs disconnected. In Figure 62 it willbe seen that the long spring is in contact with the nearer inner spring, andthe short spring is in contact with the other inner spring. These switch-springs are termed five-point switch-springs, the fifth point being thebody of the switch-spring, which is occasionally employed and serves toconnect
. The telephone system of the British post office. A practical handbook . Figure 63. curved end of the shorter spring, and the long spring rests upon the backpart of the brass peg. This raises the two outer springs off the innersprings, thus leaving the inner springs disconnected. In Figure 62 it willbe seen that the long spring is in contact with the nearer inner spring, andthe short spring is in contact with the other inner spring. These switch-springs are termed five-point switch-springs, the fifth point being thebody of the switch-spring, which is occasionally employed and serves toconnect the body of the switch-spring to the long 74 Switch-Springs, The other form of switch-spring is the eightfoint switch-spring, whichconsists of seven springs. The three additional springs B, C, D areplaced above the four springs, but at right angles to them (Figure 64).. Figure 64. The central spring carries an ebonite projection with a steel ball—restingin the body of the switch-spring. The insertion of a peg raises the ball,thus lifting the central spring from the lower to the upper spring. The Telephone System of the British Post Office. 75 CHAPTER XII. Auxiliary Apparatus. It has already been stated that two indicators—viz., the self-restoringindicator and the telephone* exchange galvanometer—are bridged acrossthe cords in order to register the ring-off signals. The telephone exchangegalvanometer (Figure 63) consists of two coils of wire mounted upon brassframes placed side by side, in the centre of which hangs a soft iron needlerendered magnetic by induction from the permanent magnet. Theaxle of the indicator passes through the permanent magnet at either end, . s L>^ B 1 Figure 65. terminating in pivots, one of which is secured in the removable pivot boxfixed to the end of the magnet and the other at the back of the coils. Theaxle is par
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
