The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 175
Fig. 166 a.—Scale f … Fig. 167.—Scale f the lifting of the drop shutter into its normal position. Thereare a large number of varieties of these instruments, the SWITCH-BOARD APPARATUS I5i simplest being those having a kind of cam projection on thefront of the drop shutter, which, when the plug is inserted inanswer to a…
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-electricengineer01inte-142-49.webp)
