American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 632
din the bridge wire. The Thomson reflecting galvanometer is described in a separatechapter. It may be added here that the beam of light should rest on the zero of thescale when no current is flowing through its coils. It may be brought to zero bymanipulating the directing magnet m, for which… … W^ INF i
Telegraph
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