Miller, Kempster Blanchard, 1870-1933 · New York : McGraw publishing company · leaf 551
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 … FIG. 379.-KELLOGG FOUR-PARTY-LINE KEY. through the opening between the plates serves to indicate to theoperator what key was last depressed. The Kellogg four-party line ringing key is shown in Fig. 379. Ingeneral form, circuits and use this key is similar to the Western 530 AMERICAN TELEPHONE…
Telephone
Internet Archive · Cornell University Library · Public Domain Mark 1.0. Free to use for anything.
