Background

Telephone wiring in the U.S. is based on pairs of conductors (individual wires) which form an electrical loop. The two conductors of a pair are twisted together so they won't separate and to enhance electrical properties. For decades, the telephone industry has relied on an established method of telling one pair from another. This method involves using 10 basic colors and combining them in a logical sequence to make 25 unique pair combinations. The colors are referred to as "Tip" and "Ring", terms which originate with the old plug-and-cord based switchboards. The plug was a phono jack type with a tip element, an insulating disk, and the shaft, or ring, of the plug. The conductors of the pair were terminated in their respective elements of the plug.

To make 25 different pairs, each tip conductor color is combined with each ring conductor color. The full sequence looks like this:

Note: Listing the tip color first is common practice for premises cables and connectivity components. However, for outside plant cables, US standards typically list the ring colors first. It doesn't make a difference; the sequence is still the same. Pair one, for example, has one white conductor and one blue conductor regardless of which you say first.

Using this method an installer can navigate pretty effectively in a 25 pair group of pairs and be able to tell one pair from another. A 25 pair group becomes the basic building block for bigger cables. How do you tell one 25 pair group from another since they both will have the same sequence of pair colors in them? Each 25 pair group, or unit, as they are also called, is loosely bound with colored binders. The binder color sequence is the same as that of the pairs, i.e., the binders for group one are colored White/Blue, for the second group are colored White/Orange, and so on. This system allows up to 600 pair cables (violet/slate binders are never used; 25 pairs x 24 units = 600 pair) to be made. Above 600 pair for all cables, and above 900 pair for cables used in the Bell and GTE systems, it gets more complicated and I'm not going to detail that here.

How does this relate to the residence? This system is not always used for wiring inside the home. Instead, a color code using green, red, black, and yellow is frequently employed. Many questions related to installing a second phone line in a home come down to confusion over mating one color code scheme with another. The table below shows how they relate to each other.

Positive Identification

Wiring for premises sometimes employs some method of marking to show which tip conductor belongs with which ring. This is referred to as positive identification and is accomplished using bandmarks or stripes. Typically a large pair count cable used in the Outside Plant (OSP) does not have bandmarks or stripes.

A bandmark is a ring of ink encircling the conductor at regular intervals. A longitudinal stripe is a narrow mark either painted down the length of the conductor or included in the color of the insulation during extrusion.

	Bandmarked
	Striped

In a white/blue pair the white conductor would have blue bandmarks (or a blue stripe) and the blue conductor would have white bandmarks (or a white stripe). Note that in a cable smaller than 6 pairs, it may only be necessary to apply bandmarks or stripes to the tip conductor (all the ring conductors will be a unique color). For premises wiring in Categories 4, 5, and higher, positive identification may not be used at all since more demanding performance requirements dictate more frequent twists per foot and the conductors of a pair stay together better.

The point is, you will probably encounter cables both with bandmarks and stripes and those without them, but the basic color codes are the same.

Use the diagram below to translate between the two schemes.
white with blue = green
blue with white = red
white with orange = black
orange with white = yellow

^{A yellow and blue "jumper" is often used for "cross-connect" between two interface points.}

 

Multi-Pair Wire & Cable  (jack diagrams are below) Base color/ Stripe color Polarity (Tip is Positive) Pair # Pin # in 25-pair "Amphenol" Connector Row # in 66 or 110 Punch-down Block White/Blue Blue/White Tip 1 Ring 1 Pair 1 26 1 1 2 White/Orange Orange/White Tip 2 Ring 2 Pair 2 27 2 3 4 White/Green Green/White Tip 3 Ring 3 Pair 3 28 3 5 6 White/Brown Brown/White Tip 4 Ring 4 Pair 4 29 4 7 8 White/Slate Slate/White Tip 5 Ring 5 Pair 5 30 5 9 10 Red/Blue Blue/Red Tip 6 Ring 6 Pair 6 31 6 11 12 Red/Orange Orange/Red Tip 7 Ring 7 Pair 7 32 7 13 14 Red/Green Green/Red Tip 8 Ring 8 Pair 8 33 8 15 16 Red/Brown Brown/Red Tip 9 Ring 9 Pair 9 34 9 17 18 Red/Slate Slate/Red Tip 10 Ring 10 Pair 10 35 10 19 20 Black/Blue Blue/Black Tip 11 Ring 11 Pair 11 36 11 21 22 Black/Orange Orange/Black Tip 12 Ring 12 Pair 12 37 12 23 24 Black/Green Green/Black Tip 13 Ring 13 Pair 13 38 13 25 26 Black/Brown Brown/Black Tip 14 Ring 14 Pair 14 39 14 27 28 Black/Slate Slate/Black Tip 15 Ring 15 Pair 15 40 15 29 30 Yellow/Blue Blue/Yellow Tip 16 Ring 16 Pair 16 41 16 31 32 Yellow/Orange Orange/Yellow Tip 17 Ring 17 Pair 17 42 17 33 34 Yellow/Green Green/Yellow Tip 18 Ring 18 Pair 18 43 18 35 36 Yellow/Brown Brown/Yellow Tip 19 Ring 19 Pair 19 44 19 37 38 Yellow/Slate Slate/Yellow Tip 20 Ring 20 Pair 20 45 20 39 40 Violet/Blue Blue/Violet Tip 21 Ring 21 Pair 21 46 21 41 42 Violet/Orange Orange/Violet Tip 22 Ring 22 Pair 22 47 22 43 44 Violet/Green Green/Violet Tip 23 Ring 23 Pair 23 48 23 45 46 Violet/Brown Brown/Violet Tip 24 Ring 24 Pair 24 49 24 47 48 Violet/Slate Slate/Violet Tip 25 Ring 25 Pair 25 50 25 49 50 Modular Jacks & Plugs Jacks and plugs are wired to conform to Uniform Service Ordering Code ("USOC") numbers, originally developed by the Bell System, and endorsed by the FCC. One specific piece of hardware can be wired in different ways, and have different USOC numbers. USOC has become an acronym, pronounced "you-sock," and jack wiring schemes are generally referred to as "USOC codes." The 8-position modular jack (above) is commonly and incorrectly referred to as “RJ45”. The 6-position modular jack is commonly referred to as RJ11, which may or may not be correct. Using RJ terms often leads to confusion since the RJ designations refer to very specific USOC wiring configurations. The designation ‘RJ’ means Registered Jack, and should be used only for jacks that are connected directly to phone company circuits. Each of the basic jack styles can be wired for different RJ configurations. For example, the 6-position jack can be wired as an RJ11C (1-pair), RJ14C (2-pair), or RJ25C (3-pair) configuration. An 8-position jack can be wired for configurations such as RJ61C (4-pair) and RJ48C. The keyed 8-position jack can be wired for RJ45S, RJ46S, and RJ47S. The fourth modular jack style is a modified version of the 6-position jack (modified modular jack or MMJ). It was designed by Digital Equipment Corporation (DEC) along with the modified modular plug (MMP) to eliminate the possibility of connecting DEC data equipment to voice lines and vice versa. (This paragraph is based on info from Siemon, a supplier of much of the telecom hardware we use and sell.) In the diagrams below, you are looking into the opening of the jack. Internal wiring in the jack may have different colors from the wiring that goes to the jack. 6 Positions 2 or 4 Wires 1 or 2 Lines RJ11 or RJ14 Jack Positions USOC RJ11 USOC RJ14 2 wht/org 3 blue/wht blue/wht 4 wht/blue wht/blue 5 org/wht 6 Positions 6 Wires 3 Lines RJ25 Jack Positions USOC RJ25 1 wht/grn 2 wht/org 3 blue/wht 4 wht/blue 5 org/wht 6 grn/wht Wires inside most phone jacks are usually solid- colored, not striped. Until a few years ago, it was customary to use "quad" solid- color wire, that matched the wires inside a jack. If you are installing a new jack, it's best to use  "twisted-pair" wire, with stripes. 8 Positions 4 or 8 Wires 4 Lines RJ61 & others Jack Positions USOC RJ61 T568A T568B (AT&T) 10BASE-T (LAN) 1 wht/brn wht/grn wht/org wht/blue 2 wht/grn grn/wht org/wht blue/wht 3 wht/org wht/org wht/grn wht/org 4 blue/wht blue/wht blue/wht 5 wht/blue wht/blue wht/blue 6 org/wht org/wht grn/wht org/wht 7 grn/wht wht/brn wht/brn 8 brn/wht brn/wht brn/wht Note: If you are going to re-use jacks previously installed for a Merlin or other ATT/Lucent/Avaya phone system that uses the T568B wiring scheme, you will either have to re-arrange the wires inside the jack, or connect the circuit that would normally go on the white/orange wire pair, to the white/green pair. Note: 8-position jacks and plugs used in Local Area Networks ("LANs") are commonly referred to as RJ45. This is incorrect, because RJ designations apply only to jacks connected to phone company circuits, not PCs or network hubs. The black diagrams and some of the info above came from Hubbell, a maker of top-quality wiring devices. We thank them.