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Outside plant is the collection of cables, poles, conduit, and fiber optics that
interconnect central offices and connect the central office to the subscribers’ premises.Cable is classified according to its supporting structure aerial cable supported on pole lines, underground cable enclosed in buried conduit and buried cable placed directly in the ground. Twisted-pair cables are classified by the wire gauge, sheath material, protective outer jacketing, and the number of pairs contained within the sheath. Cable sheath materials are predominantly high-durability plastics such as polyethylene and polyvinyl chloride. Cable sheaths are constructed to protect against damage from lightning, moisture, induction, corrosion, rocks, and rodents. Cable plant is divided into two categories in the local loop—feeder and distribution. Serving area interface terminal is junction point between the feeder and distribution cable. Protection is required for two purposes—to prevent injury or death to personnel and to prevent damage to equipment in case of lightning strike or cross with electrical power. Personnel and equipment can be protected from the hazards of unexpected contact with a foreign source of electrical potential by the following methods insulating telecommunications apparatus, shielding communications cables, grounding equipment, opening affected circuits and separating electrical and telecommunications circuits.