. Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems . sy tone. The trunk tone is generated in a very similar way to the generation ofthe busy tone. This is distributed to first selectors only. The trunk-tone wire is tapped off at each selector board and distributed through two POWER PLANT, SUPERVISORY AND TESTING EQUIPMENT 355 condensers, one for each bay. There is one wire for each mechanicalshelf of 20 switches. It runs to the primary of an induction coil so thatwhen the supervisory relay is operated, it will put this tone on the regularpositive battery fe
. Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems . sy tone. The trunk tone is generated in a very similar way to the generation ofthe busy tone. This is distributed to first selectors only. The trunk-tone wire is tapped off at each selector board and distributed through two POWER PLANT, SUPERVISORY AND TESTING EQUIPMENT 355 condensers, one for each bay. There is one wire for each mechanicalshelf of 20 switches. It runs to the primary of an induction coil so thatwhen the supervisory relay is operated, it will put this tone on the regularpositive battery feed for the line relays. Sub-office Power Equipment and Circuits.—The battery of a sub-office not more than a mile from its main exchange may be floated on themain exchange battery of 25 cells through cable pairs. If the distanceto the sub-office is too great, or the spare cable conductors not lowenough in resistance, a 120-volt rectifier installed atthe central office,as indicated in Fig. 284, may be used. Where this plan is not pract- ^ Cutoff•5 V) Charge RectifierTube. Fig. 285.—Circuits of a mercury arc rectifier charging outfit for a sub-office. icable, it is common practice to charge the sub-office batteries by meansof connections to the commercial source of power supply, tapped intothe sub-office for the purpose. If 110-volt direct current is available,the sub-office battery may be charged directly through a rheostat. Ifalternating current is available, it is customary to use a mercury arcrectifier. The circuit of a typical sub-office rectifier equipment is shown in Relays are arranged to enable the wire chief at the central officeautomatically to switch the sub-office charging apparatus on or off, asdesired, by calling certain numbers on his test-distributor switch, using acalling device on his desk. Circuits of these relays are indicated in To charge, for example, the wire chief calls 20, whereupon the 356 A U TOM A TIC TELEPHOS Y priv
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttelephone, bookyear19
