Miller, Kempster Blanchard, 1870-1933 · New York : McGraw publishing company · leaf 428
the proper private branch line,using her calling plug, and by the operation of her ringing key wouldcall the subscriber on that line. The operation of the relays A andB would remove the private branch battery from the cord circuit,and, therefore, when the private branch subscriber responded,… … FIG. 30S.—PRIVATE-BRANCH EXCHANGE LINE CIRCUIT OF CHICAGOTELEPHONE COMPANY. circuits upon the calling plug at the main office to show the mainoffice operator that the call has been responded to, and that no fur-ther action at the main office is required. The main office operator performs exactly…
Telephone
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