The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 90
h is still somewhat ex-tensively used by the PostOffice and the Railway Com-panies. It is a very largedouble - pole instrument,with a semicircular magnetfitted in a large brass case,the diaphragm being about4J inches diameter, andcorrespondingly thick. Theinstrument, although apowerful one, is too… … Fig. 54.—Scale \ 6S PRACTICAL TELEPHONE HANDBOOK
Telephone
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