Miller, Kempster Blanchard, 1870-1933 · New York : McGraw publishing company · leaf 550
n how two or more of these keys maybe associated on a single mounting strip for the purpose of securingany desired combination of keys. The means by which this key ismade into a two-way ringing key for two-party line service deservesattention. No separate indicator is used, but a knuckle joint is… … FIG. 377.—TWO KELLOGG KEYS ON SINGLE PLATE. key into the ringing position in one direction or the other. Thehandle of the key is always left leaning in the direction in which itwas last pressed, thus serving as an indicator to the touch, as well asto the vision, of the operator. The four-party line…
Telephone
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