GB277427A - Improvements in the loading of telephone transmission lines - Google Patents

Abstract

277,427. Standard Telephones & Cables, Ltd., (Western Electric Co., Inc.). June 17, 1926. Loading circuits to improve transmission.-If an entrance cable 10, Fig. 1, leading from an open-wire line 9 is uniformly loaded with coils 11, 12 .. so as to have a characteristic impedance equal to that of the line 9 thus avoiding any irregularity at the junction, the spacing of the coils 11, 12 - - does not correspond to the spacing of the loading coils 2 of a standard uniformly loaded toll cable 1 which may be routed through the same conduit. In order to avoid this inconvenience, entrance cables are, according to the invention, loaded so as to have the required characteristic frequency by means of equally-spaced alternate large and small inductance coils L1, L2, Fig. 6, which are so arranged that the large coils may be located in the existing manholes 5, 6 - , whilst the smaller coils, being of smaller size and relatively few in number can be readily housed at intermediate points. Alternatively, the coils may be of equal inductance value but spaced at alternately long and short intervals L, M as shown in Fig. 9, or unequal coils and unequal spacing may be combined. The loaded line may terminate at the mid-oipnt of a large coil L1, as shown in Fig. 6, or at the mid-point of a small coil L2, or by combination with a portion B B<1> of an equivalent uniformly-loaded line, Fig. 7, at any other position.