. American telephone practice . -board svstem to come into extended commercial use is the 322 AMERICAN TELEPHONE PRACTICE. one developed by the engineers of the Kellogg Switch-board andSupply Company and put into extensive use by that company. The line circuit, which has been the standard circuit used in theKellogg system for several years, is shown in Fig. 268. At theleft of this figure is shown the typical, simplified sub-station appa-ratus, the sub-station circuit, actually used in the Kellogg sys-tem, having already been described in Chapter XIX. The two limbsof the line extend directly to
. American telephone practice . -board svstem to come into extended commercial use is the 322 AMERICAN TELEPHONE PRACTICE. one developed by the engineers of the Kellogg Switch-board andSupply Company and put into extensive use by that company. The line circuit, which has been the standard circuit used in theKellogg system for several years, is shown in Fig. 268. At theleft of this figure is shown the typical, simplified sub-station appa-ratus, the sub-station circuit, actually used in the Kellogg sys-tem, having already been described in Chapter XIX. The two limbsof the line extend directly to two spring levers of the cut-off of these springs normally rests against a back contact pointwhen the relay is not energized, each being adapted to break thiscontact and make contact with another normally open point whenthe relay is energized. The back contact of that relay spring, whichis connected with the sleeve side of the line, is connected throughthe coil of the line relay and the common battery to the iifl FIG. 268.—KELLOGG MULTIPLE SWITCH-BOARD LINE CIRCUIT. The back contact of the spring connected with the tip side ofthe line is connected directly to ground. With the cut-off relayin its normal position, therefore, the line relay is placed under thecontrol of the subscriber in the same manner as in the line circuitof the Western Electric Company. This line relay controls a lampplaced adjacent to the answering jack. When the cut-off relay is energized the spring connected withthe tip side of the line makes engagement with a contact connectedto a wire leading to all of the tip springs of the answering and mul-tiple jacks belonging to that line, while the spring in connectionwith the sleeve side of the line engages a contact connected withall of the sleeve contacts of the jacks. The jacks have but twocontacts, a tip and a sleeve, the sleeve forming the test ring as wellas one terminal of the talking circuit. The coil of the cut
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