GB936511A - Improvements in or relating to communication cables - Google Patents

Abstract

936,511. Cables. SIEMENS & HALSKE A.G. April 11, 1961 [April 11, 1960], No. 13013/61. Class 36. [Also in Group XXXIX] A communication cable with transposed pairs comprises a conductive screen and is connected so as to simulate a coaxial circuit. A cable comprises eight insulated wires 1-8 laid around a central core of expanded polythene 108 and transposed preferably in the way disclosed in Specification 878,062, the wires being surrounded by magnetic insulation 170, e.g. of ferrite powder in polythene, a conductive screen 171, and an outer sheath 172 of synthetic material. The cable may be further served and armoured as required. The balanced pairs are connected to form two phantom and one super-phantom circuits (shown schematically at 173) and the final centre-tap is employed as the inner conductor of a coaxial circuit of which the screen 171 forms the outer conductor. In other embodiments the central core may contain a further, central, wire and may be magnetic, and the outer insulating layer may be expanded polythene. By suitable employment of phantom circuits the simulated coaxial circuit may be obtained by using as the coaxial conductors the central conductor and the superphantom centre-tap; the central conductor and the screen; or the central conductor and centre-tap in parallel, and the screen. In the latter case the central conductor may be arranged to have a potential between that of the centre-tap and the screen (Fig. 6, not shown), to minimize loss. The two-wire circuits may be used for carrier frequencies up to 250 kc/s. and the coaxial circuit up to 300 kc/s. Where the central conductor and the centre-tap are employed as the coaxial conductor, these may be transposed at intervals. Multi-core cables may be formed from a plurality of individual screened cores described above and enclosed in a synthetic or metallic sheath. The space between cores may be filled with pairs or quads, with insulating cords, or with an insulating mass.