GB296114A - Improvements in electric cables - Google Patents

Abstract

296,114. Beatty, W. E., (Bell Telephone Laboratories, Inc.). May 25, 1927. Loading or otherwise modifying circuits to improve transmission. - In a continuously-loaded signalling cable having greater inductance in some sections than in others, the capacitance of these sections is also increased in order that the characteristic impedance may remain constant, to avoid increased attenuation. The invention is described as applied to a submarine telephone (or telegraph) cable. Near the ends of the cable the inductance is reduced by the use of lighter loading; the capacitance is correspondingly increased (1) by increasing the thickness of the insulation where the cable goes rapidly into deep water, or (2) by using insulation, such as paper of lower specific inductive capacity where shallow water extends for a considerable distance from the shore. (1) The loading 11 on the central conductor 10 of permalloy at the ends of the cable is lighter than at the midsection 12, Fig. 1, and the diameter of the guttapercha 13 is increased at the ends accordingly. (2) Lighter loading 21 replaces the heavy loading 22 and paper insulation 23 replaces the guttapercha 24, the diameter of the insulation remaining substantially the same. Lead sheathing 25 is used. In a modification of (1) the thickness of insulation is varied by changing the diameter of the central conductor and its loading. In a modfication of (2) a return conductor is positioned within the lead sheath at the end sections for a distance just beyond the paper insulation and is then continued outside the sheath. The Specification discusses the theory of attenuation. Specifications 201,931; 218,261, [Class 40 (iii), Telegraphs, Electric], and 280,449 are referred to.