. The Bell System technical journal . on with thephantom circuit arrangements previously described, by means ofwhich three independent telephone circuits are derived from four 20 wires. The application of repeaters to such a group of four wires incable (spoken of as a phantomed group or a quad) is shown schemati-cally in Fig. 13. In this figure, the boxes denoted Telephone Re-peater Iepresent the complete repeater circuit shown in Fig. is necessary to separate the telephone currents of the phantom cir-cuit from those of the two side circuits by applying to the phantomgroup highly balance
. The Bell System technical journal . on with thephantom circuit arrangements previously described, by means ofwhich three independent telephone circuits are derived from four 20 wires. The application of repeaters to such a group of four wires incable (spoken of as a phantomed group or a quad) is shown schemati-cally in Fig. 13. In this figure, the boxes denoted Telephone Re-peater Iepresent the complete repeater circuit shown in Fig. is necessary to separate the telephone currents of the phantom cir-cuit from those of the two side circuits by applying to the phantomgroup highly balanced repeating coils, just as is done at the terminalsof the circuit, and providing separate repeaters for each of the two sidecircuits and the phantom as is illustrated in the figure. The figure alsoshows a typical telegraph circuit arrangement—a metallic telegraphcircuit on each pair, separated from the telephone channel by compositesets as previously described, and passing through telegraph repeatersat the telephone repeater COMPOSITEWEST SETS COMPOSITE SETS EAST Fig. 13—Showing schematically the association of the four wires of a phantom groupand composite sets, repeating coils, telephone repeaters and telegraph repeaters. Phantom operation through cables, without crosstalk between thephantom and its side circuits and between the circuits in differentquads of the cable, has involved a long train of developments indecreasing the tolerances of manufacture and increasing the uniformityin the characteristics of the cable. The cables must meet a doublerequirement, namely, freedom from crosstalk, which is made moredifiicult with the application of repeaters, and uniformity of charac-teristics to provide for suitable repeater operation. This doublerequirement has been met by niceties in design, construction, and 21 installation, including a series of delicate electrical tests on the cableand portions of the cable during the process of installation. With these developments
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
