25-pair color code
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Image:25 pair color code chart.svg
The 25 pair color code is a color code used to identify individual conductors in a kind of electrical communication wiring known as twisted pair cables. The colors are applied to the insulation that covers each conductor. The first color is chosen from one group of five colors and the other from a second group of five colors, giving 25 combinations of two colors.
- The first group of colors is, in order: white, red, black, yellow, violet.
- The second group of 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 ("1" and "2") and the pair number shown as well that maps to the pair number shown in the image and in the table further down.
The sequence of second group colors can be remembered with by the mnemonic: BOGBruSh (Blue, Orange, Green, BRown, Slate). (This mnemonic is attributed to a British radio engineer, a BOG-BRUSH being a somewhat derotatory British term for a toilet pan cleaning brush)
| Color codes | 2nd color | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Blue | Orange | Green | Brown | Slate | |||||||
| Wire # in pair -> | 1 | 2 | 1 | 2 | 1 | 2 | 1 | 2 | 1 | 2 | |
| 1st color | White | 1 | 2 | 3 | 4 | 5 | |||||
| Red | 6 | 7 | 8 | 9 | 10 | ||||||
| Black | 11 | 12 | 13 | 14 | 15 | ||||||
| Yellow | 16 | 17 | 18 | 19 | 20 | ||||||
| Violet | 21 | 22 | 23 | 24 | 25 | ||||||
(The color violet is more commonly 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, red through violet are also in spectral order, 2-7.)
Sometimes each wire in a pair will have a colored stripe or rings matching the color of its paired wire. This makes it easy to identify which pair a given wire belongs to. Otherwise, to determine which pair a wire belongs to one has to note which color codes are physically twisted together.
| Pair # | First wire | Second wire |
|---|---|---|
| 1 | White | Blue |
| 2 | Orange | |
| 3 | Green | |
| 4 | Brown | |
| 5 | Slate | |
| 6 | Red | Blue |
| 7 | Orange | |
| 8 | Green | |
| 9 | Brown | |
| 10 | Slate | |
| 11 | Black | Blue |
| 12 | Orange | |
| 13 | Green | |
| 14 | Brown | |
| 15 | Slate | |
| 16 | Yellow | Blue |
| 17 | Orange | |
| 18 | Green | |
| 19 | Brown | |
| 20 | Slate | |
| 21 | Violet | Blue |
| 22 | Orange | |
| 23 | Green | |
| 24 | Brown | |
| 25 | Slate |
When used for common analog telephone service, the first wire is known as Tip and is connected to Ground, 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.
These terms are based on the 1/4" jack plug where the "tip" of the connector is separated from the "ring" of the connector with a ring of insulation, with the longer piece of the connector being referred to as the "ring" side of the connector. The "female" side or "jack" end is normally wired with the "tip" and "ring" configuration also, to accommodate the "plug" and maintain correct polarity when connections are established.
For cables with over 25 pairs, the first 25 pairs (called a binder group) are marked with a White/Blue ribbon, the second 25 pairs with a White/Orange ribbon, and so on through the 25th binder group (625 pairs), which has a Violet/Slate ribbon. The pattern then starts over with White/Blue, and continues indefinitely.
Most telephone cabling uses only the first 4, 6 or 10 pairs and the basic pair sequence colours (as opposed to the tracer colour) can be remebered with the simple mnemonic: BOGBruSh (Blue, Orange, Green, BRown, Slate).