File:The practical telephone handbook and guide to the telephonic exchange (1906) (14756175055).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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n pulls out the plug from the trunk line,and the 24-volt battery is again connected to the line, thecurrent from it either deflecting a needle indicator connectedacross the cord at a provincial exchange end, or, if the latterclears first, causing the actuation of a 1000-ohm clearing lamprelay connected as a shunt across the connecting-cord con-ductors at the London end, as shown at R in Fig. 270, whichshows the Operators Cord Connections at the London Trunk Exchange.A black plug is used for the trunk line, and a red one for thejunction line or a second trunk line, the corresponding clearinglamps being coloured white and red. Two operators keys areprovided for each pair of cords—one a combined ringing andspeaking key for use on the trunk lines, and the other a ringingand disconnecting key for use on the junction lines, the dis-connecting part being provided to enable the operator to 264 PRACTICAL TELEPHONE HANDBOOK disconnect the junction line, and so obtain more favourable Hllllr—
Text Appearing After Image:
•^gr^y conditions for speaking on long trunk lines. For similarreasons an extra receiver is provided for each operator. Thisa TRUNK-LINE EXCHANGES 265 when not required, is hung on a hook, which disconnects it,as shown. The relay r1 works in conjunction with relay R for closingthe circuit of the clearing lamp L at night when the permanentcurrent is taken off. On the junction line side the connections are similar tothose of the ordinary C.B. junction line, a 3-point plug beingused, the sleeve of which is connected to a double cut-offrelay, r2, which when operated connects the clearing lamprelay r3 as a shunt across the junction line, the connection tothe trunk line being made through two 2 - microfaradcondensers. When connection is made to a second trunk line, the cut-offrelay is not operated, and direct connection is made betweenthe lines, the condensers being then short-circuited, as shownin the figure. There are also the usual arrangements of pilot relay andlamps, night bells, etc

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