Miller, Kempster Blanchard, 1870-1933 · New York : McGraw publishing company · leaf 151
erator. In party line working it is often necessary to make ringers thatwill respond to only one direction of current; that is, to impulsesof one direction only, whether positive or negative. This is accom-plished by adding to the ordinary ringer= a little coiled spring MAGNETO CALLING APPARATUS.… … FIG. 104.—DIAGRAM OF BIASED BELL. been put into practice, probably the best form being that whereina linen or silk thread tied to the free end of the spring is woundaround a screw in a similar manner to the method used in adjusting
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