File:The practical telephone handbook and guide to the telephonic exchange (1906) (14569489110).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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lling plug fromthe junction-line jack the armature of the 12,000-ohm relayat the incoming end falls back, breaking the shunt acrossthe clearing lamp, which lights, and gives the clearing signalto the B operator to disconnect. When the B operatorwithdraws the junction-line plug, the armature of relay oreturns to the normal position, and the clearing lamp goesout. Fig. 257 illustrates a complete connection when in theringing condition. At the outgoing end the supervisory lampin the answering plug circuit is shunted out by relay a, as thesubscriber has his telephone ofE the rest. The called sub-scriber at the b exchange has his telephone on the rest, andas the operator has depressed the machine ringing key nthere is a circuit from the earthed generator, through interrupters and front coil of relay G, through outer contact of keyN and lower contact of relay J to ring of plug, and thence roundinstrument to tip of plug, contacts of relays o and J, key n. and 244 PRACTICAL TELEPHONE HANDBOOK
Text Appearing After Image:
earth. The bell is«.therefore, rung; butthere is not sufficientcurrent to actuaterelay g, and the mac-hine key is held downby electro - magnetcoils l, which areenergised by currentfrom battery throughcontact of relay g, keyN, sleeve of plug andbush of jack to cut-off relay p and earth.When the telephoneat t is removed fromthe rest, the increasedringing current actu-ates relay g. Thisopens circuit throughL, thus releasingplunger of key n,which flies back to thenormal position. During the time thesubscriber is being-rung there is no cir-cuit through relay sand therefore the12,000-ohm coil ofrelay d is not shuntedby low-resistance coile, and consequentlyrelay b is also openand the calling super-visory lamp at the aend of circuit is alight. JUNCTION-LINE WORKING 245 The interrupt? con-nects up the ringerfor three seconds andthen earth for threeseconds. If the sub-scriber t removes histelephone from the restduring an interval inthe ringing, the relais still actuated by the24-volt ba tery

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