The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 472
ative pole ofthe battery and the B end of the wire are shown con-nected to earth, which is taken as at zero potential. In the practical instrument a galvanometer is used as thebridge, and the more sensitive this is the more accurate thetest can be made. The bridge and resistances are… … Fig. 416.—Skeleton Diagram of Wheatstone Bridge up of a, a known resistance, and r, an adjustable resistance.The battery key b is provided so that the battery may beconnected when required, and the key G (which should be
Telephone
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