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Subscriber LinesThese lines (or loops) connect the subscriber station equipment and telephone set to the central office. A telephone dropref.1 of insulated paired wires extends from the terminals of the interior wiring of the telephone station to the aerial cable box. The various aerial cables are brought together and spliced into larger cables leading to the central office. These cables terminate in an "underground" cable box where the aerial and underground cables are connected, usually through suitable protection to prevent the exposed aerial cables from bringing hazardous currents or voltages into the underground cables (page 568). If the cable terminals are a considerable distance from the location of the telephone set, a few spans of iron open wire are often installed instead of making the entire connection of paired conductors. The cables (page 250) used are paper insulated and have lead or plastic sheaths (page 236). The development of exchange cable is shown in Table I. Experimental workref.14 has been done on having 3030 pairs of No. 28 A.W.G. wires in a standard 25/8-inch outside diameter sheath. Cables having such small conductors can be used only in congested areas where the subscriber lines are short. For longer lines, larger conductors must be used, so that the transmitters will receive sufficient direct current from the central office and so that the losses to the speech currents will not be too large.
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Last Update: 2011-05-27