File:The practical telephone handbook and guide to the telephonic exchange (1906) (14569540018).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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relay. This relay is actuated by the in-sertion of the plug into the jack of the called line, thus con-necting the sleeve and the third conductor of the cord toearth. Under normal conditions the tip is connectedthrough the outer contact of the relay through an order-wiretransfer key to a tertiary winding of the operators inductioncoil, so that the engaged test can be made through the tipof the plug without introducing an earth connection on to theordinary line circuit, Directly the plug is inserted in the 25o PRACTICAL TELEPHONE HANDBOOK jack, the test connection is cut off by the operation of therelay. The same relay when actuated puts an earth con-nection on the centre of a double-wound retardation coil of1000 ohms total resistance, the connection passing throughthe coil of a clearing relay. The called subscriber gives the clearing signal by ringingover the loop with his generator, this dropping the clearing To Wd Coil. a$ N txt Position.*ToNextPosiU°f OuujoUgEnd jjjjji ^^ppj^JHSr
Text Appearing After Image:
Pilot Relai^ rig. 262.—Order-Wire Junction between Magneto Exchanges indicator at the outgoing or originating end, but notaffecting the clearing relay at the incoming end of the junctionline. The operator at the outgoing end disconnects, and thearmature of relay R completes the connection of the earthedbattery to the A wire of the junction line. The currentpasses through one half of the retardation coil, and throughthe clearing relay, and causes the lighting of the clearing lamp.The B operator then disconnects. The withdrawal of the JUNCTION-LINE WORKING 251 plug causes a break in the 250-ohm relay, and the falling backof the armature breaks the circuit of the clearing battery atthe outgoing end through the clearing relay at the incoming end. It will thus be seen that the control of the connection isleft with the A operator at the originating exchange. The instructions for connection are, of course, given overthe order wire, as already described, the connections of theorder wire bei

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