The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 203
their jacks. Small Switch-Boards for Central Battery Sub-Exchanges.— r78 PRACTICAL TELEPHONE HANDBOOK Small switch-boards are often needed for sub-exchanges ofan unimportant nature working in conjunction with a maincentral battery exchange. In such cases the method to beadopted for the supply of… … Fig. 204 current could be supplied to the extension instruments throughthe junction lines. It is, however, necessary to provide alsofor the extension lines being connected one to another. Theprovision of storage cells in such cases is out of the question,for many reasons. For such cases current has…
Telephone
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