The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 208
09, the terminals marked + and-being then unlooped from each other. CHAPTER XIII LARGER SUB-EXCHANGE AND PRIVATE BRANCHEXCHANGE SWITCH-BOARDS The switch-boards so far described have been intended tosupply the wants of small central offices or private exchangesof not more than about 25 lines, where… … Fig. 210 which special provision is made for rapid operating and forthe effective supervision of the connections. Standard Board.—Figs. 212 and 213 give views of a 50-lineswitch-board (arranged for magneto working) as used by theNational Telephone Co. It is worked on the double-cord principle, the…
Telephone
Internet Archive · Northeastern University Library · Public Domain Mark 1.0. Free to use for anything.
![An illustration from [Electric engineering.] (1902)](https://img.insideoutlibrary.com/img/200/ia-electricengineer03inte-313-191.webp)
