. American telephone practice . metallic circuit formed by the two connectedlines. While the subscribers receivers are removed from the hooksthe current from battery, B, flowing through the sleeve strand of thecord circuit energizes the magnets of the clearing-out anunciators,K2 and K3, and causes them to lift their targets. As soon as eithersubscriber hangs up his receiver this current ceases to flow, becausethe line wire, with which the sleeve strand is connected, is opened atthe hook. This allows the target of the annunciator, K2 or K3i tofall, showing that that subscriber has ceased to use
. American telephone practice . metallic circuit formed by the two connectedlines. While the subscribers receivers are removed from the hooksthe current from battery, B, flowing through the sleeve strand of thecord circuit energizes the magnets of the clearing-out anunciators,K2 and K3, and causes them to lift their targets. As soon as eithersubscriber hangs up his receiver this current ceases to flow, becausethe line wire, with which the sleeve strand is connected, is opened atthe hook. This allows the target of the annunciator, K2 or K3i tofall, showing that that subscriber has ceased to use his insrument. This represents, perhaps, the highest development attained in anyof the methods for centralizing all sources of energy in telephonesystems by feeding over the two sides of the line in multiple. A line circuit wherein the lamp signal is connected directly in theline instead of in the local circuit of a relay, as is usual, is shown inFig. 2^2. This is also interesting as showing a practical application UlHC LXMf». A^SJACK STATION^ FIG. 252.—LINE CIRCUIT WITH ELECTROLYTIC CELL. of the scheme already mentioned of placing a secondary battery at the sub-station charged from the central office over the line circuit. In this the subscribers apparatus is shown at the left, and thecentral-office apparatus at the right. The line wire, 2, forming oneside of a metallic circuit, is connected with the tip-spring of the jack,and passes through an incandescent lamp, /, and through an inductiveresistance, h, to one pole of a battery, B. The other side, 3, of themetallic circuit passes through an inductive resistance, g, to the otherpole of the same battery. When the subscribers receiver is on itshook the circuit at the subscribers station between the two sides ofthe line wire is completed only through the high-resistance call-bell,e, and as this bell has a resistance of about 1000 ohms, the current 302 AMERICAN TELEPHONE PRACTICE. from the battery through the line circuit is n
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