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Armour: Steel wire armour provides mechanical protection, which means the cable can withstand higher stresses, be buried directly and used in external or underground projects. [4] The armouring is normally connected to earth and can sometimes be used as the circuit protective conductor ("earth wire") for the equipment supplied by cable.
Cross-section of direct buried cable. Direct-buried cable (DBC) is a kind of communications or transmissions electrical cable which is especially designed to be buried under the ground without any other cover, sheath, or duct to protect it. [1] Most direct-buried cable is built to specific tolerances to heat, moisture, conductivity, and soil ...
The conduit methods were known to be of better quality, but cost significantly more than K&T. [2] In 1909, flexible armored cable cost about twice as much as K&T, and conduit cost about three times the price of K&T. [6] Knob and tube wiring persisted since it allowed owners to wire a building for electricity at lower cost.
It has advantages over armored building cable because it is lighter, easier to handle, and its sheathing is easier to work with. [10] Power cables use stranded copper or aluminum conductors, although small power cables may use solid conductors in sizes of up to 1/0. (For a detailed discussion on copper cables, see: Copper wire and cable.). The ...
Cables usually are secured with special fittings where they enter electrical apparatus; this may be a simple screw clamp for jacketed cables in a dry location, or a polymer-gasketed cable connector that mechanically engages the armour of an armoured cable and provides a water-resistant connection.
A similar, usually wall mounted, container used mainly to accommodate switches, sockets and the associated connecting wiring is called a pattress. The term junction box may also be used for a larger item, such as a piece of street furniture. In the UK, such items are often called a cabinet. See Enclosure (electrical).
Several other types of wiring systems are used for building wiring in the United States; these include corrugated metal armored cable, mineral-insulated cable, other types of power cable, and various types of electrical conduit. In industrial applications cables may be laid in cable trays. Cable type TC is especially intended for use in tray ...
Cables jacketing materials can be formulated to prevent fire spread [4] (see Mineral-insulated copper-clad cable). Alternately, fire spread amongst combustible cables can be prevented by the application of fire retardant coatings directly on the cable exterior, [5] or the fire threat can be isolated by the installation of boxes constructed of ...