Design of polyethylene-insulated multipair telephone cable

Cables are designed to have special characteristics which will make them suitable for particular uses or purposes. In the case of telephone cable the purpose is primarily to transmit information at voice and carrier frequency during an expected life of approximately 30 years. To achieve this, certain mechanical and electrical characteristics must be built into the cable. Mechanical characteristics include such characteristics as resistance to environmental factors including heat, cold, wind, lightning, moisture, sunlight, and oxygen, as well as resistance to damage by rodents and insects, and by workmen. Other desirable mechanical characteristics involve factors of convenience of manufacture, installation, and joining.