. American telephone practice . es being traced from a to spring b, which bearsagainst the terminal pin of the armature, thence from the wire, c, MAGNETO CALLING APPARATUS. 117 forming the winding, to the frame, d, of the generator, and to thewire, c. »Its path, however, is normally short-circuited by meansof the manually-operated spring, k, normally resting against theback contact, g, in such manner as to complete a circuit of prac-tically no resistance between the terminals, a and e. Under suchcircumstances, any currents coming over the line would follow theshunt path rather than traverse th
. American telephone practice . es being traced from a to spring b, which bearsagainst the terminal pin of the armature, thence from the wire, c, MAGNETO CALLING APPARATUS. 117 forming the winding, to the frame, d, of the generator, and to thewire, c. »Its path, however, is normally short-circuited by meansof the manually-operated spring, k, normally resting against theback contact, g, in such manner as to complete a circuit of prac-tically no resistance between the terminals, a and e. Under suchcircumstances, any currents coming over the line would follow theshunt path rather than traverse the armature. Pressure on thebutton, h, however, will break the shunt path, under which circum-stance a current generated in the armature winding, upon operatingthe generator, would pass to line, not being able to traverse theshunt path. Automatic devices have now almost entirely supplanted the man-ual, as the latter were never satisfactory, owing to the inability orignorance of careless persons to properly manipulate them. Many. FIG. 87.—AUTOMATIC SHUNT. styles of these automatic shunt devices have come into general use,the one shown in Fig. 87 being typical. This particular shunt wasintroduced by the Western Electric Company in the early days oftelephony. Referring to this figure, a and e represent the terminalsof the generator, the path between them through the armature beingtraced from the terminal, a, through the lower portion of the spring,b, which bears against the armature pin, thence through the wind-ing, /, of the armature and the frame of the generator to the ter-minal, c. When a generator is not being operated, however, a low-resistance shunt exists around the armature which may be tracedfrom the terminal, a, through the upper portion of spring, b, whichrests against the end of the shaft, s, which in turn is in contactwith the terminal, e, through the bearing plates, c and d, to the frameof the machine. 118 AMERICAN TELEPHONE PRACTICE. The large gear-wheel, G, is l
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