Miller, Kempster Blanchard, 1870-1933 · New York : McGraw publishing company · leaf 551
ey. The indicating feature for the ringing keys in this is interest-ing, consisting as it does of four slidable plates adapted to bemoved in one direction or the other by the operation of any one of MULTIPLE SWITCH-BOARD APPARATUS. 529 the plungers. As these plates all bear against each other… … FIG. 378.—WESTERN ELECTRIC FOUR-PARTY-LINE KEY. operated, it follows that an opening will always be left between thepair of plates corresponding to the plunger last depressed. Thesurface below the plates is painted a bright red, and this showing
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