GB453124A - Improvements in or relating to multi-conductor electric telephone cables for carrier current communication - Google Patents

Abstract

453,124. Cables. STANDARD TELEPHONES & CABLES, Ltd., BAGULEY, E., and LONG, A. L., Connaught House, Aldwych, London. March 1, 1935, No. 6532. Drawings to Specification. [Class 36] A multi-conductor telephone cable for carrier current working comprises two or more layers of twisted cores (pairs, quads, &c.) enclosed in a lead sheath which is spaced radially from the cores by means of a layer of dielectric material of a thickness greater than would be necessary for mechanical or electrical breakdown requirements, the thickness of such layer being critically determined so that the transmission characteristics at carrier frequencies of the cores nearest the lead sheath are substantiaily the same as those of the cores in the centre or inner layers of the cable lay-up, whereby the unequal influence of the lead sheath upon the cores at carrier frequencies is reduced. A thin conducting layer of metal tape or metallized paper may be interposed at a critically determined position in the space between the cores and sheath such that the mutual capacities of the outer layer cores are made substantially the same as those of the centre and inner layers without substantially affecting the previously equalized A.C. resistances of said cores ; the control of the mutual capacities may be effected by varying the overlap or position or both of the conducting layer with respect to the cores ; such layer may be positioned immediately over the outermost core layer.