The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 159
essed between any one of the three pairs of switch-springs—1, 2 and 3. This causes the springs to be lifted from the innerto the outer spring contacts. Normal; Exchange to Main and Extension—In thenormal position, as shown in the figure, the extension andmain instruments are connected in bridge to… … To MAIN INST. Fig. 150.—Connections for Single Extension with Intercommunica-tion-Magneto Calling in No. 1 switch the extension line is cut off the exchange andjoined to the extra bell through the condenser, while the main remains connected to the exchange line withoutthe possibility of being…
Telephone
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