The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 332
lated metal strips, arrangedlongitudinally, so as to form a cylinder. Metal or carbon brushes for collecting the current are arranged to bearon the strips at opposite sides, so as to form the commutator.Without such an arrangement alternating currents would bedelivered from the machine. The figure… … Fig. 306 employed, these being energised by the generated currentitself. It is found possible to start the current in such machineswithout the help of outside current, owing to the fact that acertain amount of residual magnetism is always found in theiron cores of electro-magnets. This starts a…
Telephone
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