|
The 25-pair color code is a color code used to identify individual conductors in twisted pair wiring for telecommunications. The colors are applied to the insulation that covers each conductor. The first (or major) color is chosen from one group of five colors and the other (or minor) color from a second group of five colors, giving 25 combinations of two colors. The code is often seen in RJ21 cables. ==Overview== * The first group of (major) colors is, in order: ''white, red, black, yellow, violet''. * The second group of (minor) colors is, in order: ''blue, orange, green, brown, slate''. The 25 combinations are shown to the right in the image. The combinations are also shown in the table below showing the color for each wire and the pair number.〔〔 In addition to the pair number, the pairs may also be referred to by their color codes as the "major/minor" or "major-minor" pair (e.g. pair #9 is called the "red/brown" or "R-BR" pair). The first five combinations (i.e. the white group) are very common in telecommunications and data wiring worldwide, but beyond that there is considerably more variation. The color ''violet'' is sometimes called purple, but in the telecommunications and electronics industry it is always referred to as violet. Similarly, ''slate'' is a particular shade of gray. The names of most of the colors were taken from the conventional colors of the rainbow or optical spectrum, and in the electronic color code, which uses the same 10 colors (though in a different order). Usually (unlike the second picture above), each wire in a pair will have a colored stripe, dots, or rings (often called a "tracer") matching the color of its paired wire (as shown in the first picture above). This makes it easy to identify which pair a given wire belongs to, giving each wire in a 25-pair cable its own unique colors. This means that the first pair is a mate of white with a blue tracer and a colour wire of blue with a white tracer. Pair 17 would be a mate of yellow with an orange tracer and a colour wire of orange with a yellow tracer. In cables that do not employ this scheme, to determine which pair a wire belongs to, one has to note which color codes are physically twisted together in the lay of the cable as the sheath is stripped back, since there are multiple wires of each color in the cable (e.g. a 12-pair cable using just the solid color scheme would have 5 white, 5 red, 2 black, 3 blue, 3 orange, 2 green, 2 brown, and 2 slate wires). When used for common analog telephone service, the first wire is known as "tip" and is connected to the positive side of the direct current (DC) circuit, while the second wire is known as "ring" and is connected to the negative side of the circuit, following the tip and ring convention. Neither of these two wires has any connection to the local ground. This creates a balanced audio circuit with common-mode rejection also known as a differential pair. This convention works in the UK with the first or mate wire as the positive A leg and the colour wire as the negative B leg. These terms are based on the s, which were employed in telephone switchboards in the 19th and 20th centuries, where the "tip" contact of the connector is separated from the "ring" contact by a ring of insulation. The connection furthest from the cable is known as the "tip", the middle connection is the "ring", and the (largest) connection closest to the wire is the "sleeve" (unused in this case). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「25-pair color code」の詳細全文を読む スポンサード リンク
|