Abstract: In the manufacture of a cable having a plurality of filamentary members such as wires, optical fibres or the like within an extruded thermoplastic sheath the members are twisted into a periodically reversing helical configuration immediately prior to the extrusion of the sheath around them, and the extruded sheath is rapidly cooled on emergence from the extruder head so as to cause the extrudate to set and thereby retain the members in the twisted condition.

Abstract: An optical fibre cable has a plurality of longitudinally extending closed channels (6) formed in a protective cover, and each bounded by part of the outer wall (5) of the cover, wherein said wall (5) is formed with at least one region (8) of reduced thickness extending along a channel (6) so as to form a line of weakness which facilitates penetration of the cover to give access to the optical fibre (7) or fibres within the channel (6). A rip cord (9) may be embedded in the wall (5) so that by pulling the rip cord (9) a slit (10) is formed in the wall (8).