JUNCTION LINE FILTERS

Abstract

TWO articles on these filters by F. A. Hinshaw and J. O. Israel respectively (Bell Lab. Rec., 20, No. 9, May 1942) describe their design and applications in communication circuits. Open-wire lines brought into repeater stations or toll offices located in densely populated areas are usually terminated at the outskirts of the area, and the circuits are brought to the office through cables. These cables are usually loaded so as to improve the impedance match between the open-wire line and the cable and to reduce the loss in the cable. At repeater stations and terminals the separation of the carrier and voice circuits is ordinarily accomplished by niters at the office end of the cable. It is not feasible to use the office filters to separate the carrier and voice circuits at the terminal pole to avoid the necessity of carrier loading. Moreover, difficulties would be encountered in obtaining a suitable balance at the voice repeater because of the imperfect impedance match of filter and cable, and of the length of cable between filter and repeater, which would be different for each installation.