Telephone cable has plastics-insulated conductors. The hollow space in the sleeved core and between it and the sleeve is filled with a water-impermeable mass of polyisobutylene or atactic polybutene of medium m.wt. contg. hollow pref. ethylene/vinyl chloride copolymer spheres 2-200 mu in dia. Pref. the mass is blended with natural or synthetic waxes and/or resins.
