Course 4: Specialized Cables
Jackets & Insulation
Jacket
The two most common types of cable jacket material used to house the internal conduction material are PVC (Polyvinyl chloride) and Plenum. The decision between PVC and Plenum is dictated largely by cost (plenum is more expensive) in proportion to the value it offers in certain environments.
PVC: Also referred to as Vinyl, PVC provides an inexpensive means of housing cables, and offers excellent durability while remaining practically pliable.
Plenum: Not as commonly used as PVC, Plenum jacketing gets its name from the environment for which it is designed. Used in compartments or chambers to which one or more air ducts are connected, and [which] form part of the air distribution system of a building, Plenum jacketed cable is less prone to allowing a fire to travel along the length of the cable – spreading the damage to other building locales.
Insulation
To help minimize signal loss due to Electro-Magnetic Interference (EMI) and other environmental factors, most cable cores are housed in an insulating material within the external jacket; system configuration, the type(s) of signals being transmitted and the cable proximity to sources of interference must be taken into account.
Two examples of cable shielding styles are Braided shielding and Foil shielding.
Braided Shielding provides excellent structural integrity. As the name implies, braided shielding consists of plastic or metal shielding that has been braided across the length of the cable core. Generally, the higher the percentage of braid coverage, the more effective the shield.
Foil Shielding on the other hand, is comprised of aluminum foil that has been tightly wound around the core of the cable. Foil shields provide complete coverage of the core circumference, for superior protection against environmental interference from surrounding devices. The thin composition of the foil allows for multiple cores within the external jacket to be insulated separately from one another.
In contrast to braided insulation, foil insulated cables weigh less, are less costly than braided cable, as well as more flexible.
Next – Chapter 4 - Specialized Cables
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