The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 302
les from the unbalancing of the lines,and for other reasons. For such reasons the condensermethod of ringing is much preferable when it can be used. Thomson & Robes System.—This is a modification of theHibbard system, designed to dispense with the need for directearth connections on the lines.…
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-electricengineer04inte-361-156.webp)
