American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 61
nish positive polarity, the other series, negative polarity. Toguard against failure of one of the series, a third series of 5 machines is held in readi-ness as a spare series. Suitable devices for converting the spare series into a pos-itive or negative polarity series, are provided in the dynamo… … DYNAMO REVERSING SWITCH. here that this result, namely, the conversion of the spare series into a positive ornegative series, can be readily accomplished by placing a reversing switch in the fieldmagnet circuit of the machines, since a cliange in the direction of the current throughthe field magnet…
Telegraph
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