File:American telephone practice (1905) (14569615330).jpg

Identifier: americantelepho00mill (find matches)
Title: American telephone practice
Year: 1905 (1900s)
Authors: Miller, Kempster B. (from old catalog)
Subjects:
Publisher:
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
The relay, T, is also actuated to prevent any pos-sible lighting of the line lamp, S, upon the other division of theswitch-board. At the same time the spring, 3, of relay R and spring,6. of relay T engage their forward contacts, 15 and 16, and completethe metallic talking circuit from the line conductors, 1 and 2, to thetip and sleeve conductors leading to the jacks. If the line calledfor is idle, the plug is inserted in the proper multiple jack and theringing key is actuated. The insertion of the plug closes a pathfor current from the battery, B, over the sleeve of the cord circuitto the winding, 17, of relay T, winding, 18, of relay R to ground, thusactuating both relays, and rendering the line signals of both di-visions of the board inoperative, and also connecting the spring-jackcontacts of the line to the external line conductors. The operationof the ringing key does not effect any re-arrangement of the relays,R and T, for the reason that the sleeve side of the key closes a cir-
Text Appearing After Image:
393 394 AMERICAN TELEPHONE PRACTICE. cuit from the battery, B2, through the resistance, 19, to the sleeveconductor of the jack. The operation of testing and of the supervisory signals, and, infact, of the cord circuit as a whole, is the same as in the single di-vision two-wire system of the Kellogg Company. The part that the divided multiple board is to play in the futuredevelopment of telephony is now the subject of much discussion.A few years ago there seemed to be a decided need for this systemon account of the then present limit of the straight or single divisionmultiple board to approximately 6000 lines. With the advent ofthe three-wire multiple board, as developed by the Western ElectricCompany, by which the size of the jacks are reduced to f inch be-tween centers, and the further simplification resulting in the pro-duction of the two-wire system, with its 3-10-inch or ^-inch jacks,the capacity of the single division multiple board has been increasedto such an extent as to make

Note About Images