Miller, Kempster Blanchard, 1870-1933 · New York : McGraw publishing company · leaf 443
vate branch end of the trunk, will be restored to its normal posi-tion and allow its armature to fall back, thus lighting the disconnectlamp, which is now included in the circuit which may be tracedfrom the live side of battery to the front contact of the relay B.thence through the lamp and back… … FIG. 317.—PRIVATE-BRANCH EXCHANGE SWITCH-BOARD. which may be done by merely throwing her telephone in circuit bymeans of her listening key. It may also be done by plugging in to theshort-circuited jack. In Fig. 316 is shown a type of private branch exchange boardwhich is representative of good…
Telephone
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