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For cables, the swapping is gradual and continuous; that is the two or three conductors are twisted around each other. For communication cables, this is called twisted pair . For overhead power lines or open pair communication lines, the conductors are exchanged at pylons, for example at transposition towers or at utility poles , respectively.
The 20-pair colour code is a colour code used in Australia to identify individual conductors in a kind of electrical telecommunication wiring for indoor use, known as twisted pair cables. The colours are applied to the insulation that covers each conductor. The first colour is chosen from one group of five colours.
Telephone cable containing multiple twisted-pair lines. The primary line constants are parameters that describe the characteristics of conductive transmission lines, such as pairs of copper wires, in terms of the physical electrical properties of the line.
Twisted-pair cabling was invented by Alexander Graham Bell in 1881. [4] By 1900, the entire American telephone network was either twisted pair or open wire with transposition to guard against interference. Today, most of the twisted pairs in the world are outdoor landlines, owned and maintained by telephone companies, used for voice service.
In electrical engineering, star-quad cable is a four-conductor electrical cable that has a special quadrupole geometry which provides magnetic immunity when used in a balanced line. [1] Four conductors are used to carry the two legs of the balanced line. All four conductors must be an equal distance from a common point (usually the center of ...
Typical values of Z 0 are 50 or 75 ohms for a coaxial cable, about 100 ohms for a twisted pair of wires, and about 300 ohms for a common type of untwisted pair used in radio transmission. Propagation delay is proportional to the length of the transmission line and is never less than the length divided by the speed of light .
The wire pairs are referenced directly by their color combination, or by the pair number. For example, pair 9 is also called the red-brown pair. In technical tabulations, the colors are often suitably abbreviated. Violet is the standard name in the telecommunications and electronics industry, but it is sometimes referred to as purple.
A coaxial cable has a central conductor surrounded by a sheath of conductor with insulation in between. Coaxial cables form a transmission line and confine the electromagnetic wave to an area inside the cable between the center conductor and the shield. The transmission of energy in the line occurs totally through the dielectric inside the ...