File:The practical telephone handbook and guide to the telephonic exchange (1906) (14755952562).jpg

Identifier: practicaltelepho00pool (find matches)
Title: The practical telephone handbook and guide to the telephonic exchange
Year: 1906 (1900s)
Authors: Poole, Joseph
Subjects: Telephone
Publisher: New York, Macmillan Co.
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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Text Appearing Before Image:
TO SKOBO UNE OF BOARDi i*go£=a, flS*3!^0, P»«TY DNESliSSMIftfHSMULTIPLE ,Qmswcti»cjack TOCftuiitBjuiPMnn V - Cftaiieiwap W Fig. 516.—Connections for Double-Jack Party-Line Working ture of line relay closes contact s, completing battery circuitthrough contact of cut-off relay ur, lamp al, pilot relay(not shown) and earth back to battery. The operator theninserts answering plug ap into answering jack lj, which closes amomentary battery circuit through supervisory lamp (or lamprelay) sl, sleeve contact of answering plug ap, socket ofanswering jack lj, coil of cut-off relay ur to earth. The arma-ture of ur is attracted and the calling lamp (or relay) is cutoff; and at the same time the supervisory lamp is short-circuitedby the front contact of ur relay and a new battery circuit APPENDIX 573 completed through contact s for the coil of relay ur. Theconnection to the called-for subscriber is completed in the
Text Appearing After Image:
Fig. 517.—Connections of L. M. Ericssons C.B. System usual manner by connecting into one of the multiple jacks mj,and the speaking circuit is completed through two condensers.The operator is provided with combined listening and ringing 574 APPENDIX keys, and the latter keys are arranged for automaticworking. The current for speaking is fed through coils e2 and R1? andis not interrupted so long as the receiver is off the hook at thesubscribers instrument, so that the annoying clicks which areheard in other C.B. systems are absent in the Ericsson one. Whilst the receiver is off the hook the supervisory lamp (orrelay) sl is short-circuited by front contact of cut-off relay ur,but on hanging up the receiver the battery circuit through relayR is broken, contact s is opened, and the short-circuit removedfrom the supervisory lamp, which in consequence glows. For the engaged test the operators headgear receiver isdifferentially wound with a centre connection to earth or tothe negative side

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