Miller, Kempster Blanchard, 1870-1933 · New York : McGraw publishing company · leaf 274
would cause the relay to let go of its armature, and thus breakthe circuit at point h. The white lamp remains lighted, therefore,as long as the call on its A trunk is unattended to. The first act of the A operator on seeing this light is to throwher lever corresponding to that light into its… … FIG. 219.—TABLE OF A BOARD. be noted that these keys on the A operators board are the onlymeans afforded to any operators for communicating with sub-scribers. The operation of this key breaks the circuit of the whitelamp at the points, c f. As soon-as the listening key is thrown againinto its…
Telephone
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