Insulated cable is one which has an insulator covering over the conductors. Insulated cable generally has a voltage rating per industry standards. The rating is based upon the insulating material properties, its thickness, and the intended use of the cable.

In the 19th century and early 20th centuries, cable was often insulated using cloth, rubber and even paper. Plastic materials are generally used today, except for high reliability power cables.

There are 4 types of plastic insulation used n telecommunications cables today: solid, cellular, foam skin and skin-foam-skin.

Each has its strengths and weaknesses. For protection against water ingress to the copper which is the most problematic issue for telephone companies then plain cellular should not be used. The best barrier is a metallic sheath.

85% of US production is foam skin today. The skin provides a barrier to moisture ingress and the foam/cellular insulation has air cells which improve the transmission capability of the cable conductors.

Cables