GB434855A - Improvements in and relating to electric telephone cables for four-wire circuit operation - Google Patents

Abstract

434,855. Cables. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Sept. 27, 1934, No. 27763. Convention date, Oct. 2, 1933. [Class 36] To reduce crosstalk between conductors of the same group in a telephone cable for four-wire circuit operation of the kind in which the conductors of the two directions of transmission are arranged in separate groups, some or all of the conductors of each group are electrostatically or electromagnetically screened from one another, the arrangement of the screens being the same in both groups. The screens, which may consist of conductive or semiconductive tape wound in open helices around the conductors to be screened, may be applied only to those conductors which have electrical constants different from those of the remainder of the group. Fig. 1 shows a cable having a core 10 of conductors for two-wire working which is surrounded by arcuate groups 13, 14 of conductors arranged for four-wire operation. The groups 13, 14 are separated by conducting screens 15, 16 and the layers of conductors in the group 13 are separated from one another by screens 17, 18. Screens 19, 20 are also provided in the group 14. In a similar construction the arcuate screens 17-20 are replaced by radial screens and the screens 15, 16 are both conducting and magnetic. In another construction the groups 13, 14 each consist of six circular conductor groups which are laid around the core 10, each circular conductor group comprising a central screened pair for long distance traffic, and an outer layer of six ordinary quads. Fig. 3 shows screened pairs 43, 44 constructed for fourwire carrier frequency operation which are disposed respectively in screened core groups 40, 41. The groups 40, 41 may contain additional screens 47, 48.