Telephone Technical Support Page
 
 
This FAQ page is for telephone cabling questions.  Also see the Networking technical support (FAQ) page.

 

TELEPHONE (VOICE) FAQs
AT&T COLOR CODE (25 PAIR)
DSL circuit wiring
ISDN circuit wiring
T1 circuit wiring
T-568A COLOR CODE
T-568B COLOR CODE
USOC COLOR CODE
 

AT&T telephone color code for 25 pair cable

Pair Primary (tip) Secondary (ring)
1 White/Blue Blue/White
2 White/Orange Orange/White
3 White/Green Green/White
4 White/Brown Brown/White
5 White/Slate Slate/White
6 Red/Blue Blue/Red
7 Red/Orange Orange/Red
8 Red/Green Green/Red
9 Red/Brown Brown/Red
10 Red/Slate Slate/Red
11 Black/Blue Blue/Black
12 Black/Orange Orange/Black
13 Black/Green Green/Black
14 Black/Brown Brown/Black
15 Black/Slate Slate/Black
16 Yellow/Blue Blue/Yellow
17 Yellow/Orange Orange/Yellow
18 Yellow/Green Green/Yellow
19 Yellow/Brown Brown/Yellow
20 Yellow/Slate Slate/Yellow
21 Violet/Blue Blue/Violet
22 Violet/Orange Orange/Violet
23 Violet/Green Green/Violet
24 Violet/Brown Brown/Violet
25 Violet/Slate Slate/Violet

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RJ-45 wiring guide (TIA 568B or AT&T)

The 568B wiring is used in almost 90% of  installations.   The pin numbers refer to a RJ-45 telephone type connector.  Pin #1 is the one on the left when you hold the tab down with the wire facing you, as you would plug it in.   Pin #2 is the next one on the right and lastly, pin #8 is the one all the way to the right. 

PIN #    COLOR                SCREW TYPE COLOR

  1.     White/Orange        Blue
  2.     Orange/White       Orange
  3.     White/Green          Black  
  4.     Blue/White            Red
  5.     White/Blue            Green
  6.     Green/White          Yellow
  7.     White/Brown          Brown
  8.     Brown/White          White (or gray)
T568b.jpg (7119 bytes)  NOTE: This is an RJ-45 wall plate (front view), T568B.

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RJ-45 wiring guide (TIA 568A)

The 568A wiring is used when compatibility to telephone wiring systems (USOC) is needed.  It is not recommended, as parts are not as commonly available.

PIN #    COLOR                    SCREW TYPE PLATE

  1.     White/Green                Blue
  2.     Green/White                Orange
  3.     White/Orange              Black
  4.     Blue/White                  Red
  5.     White/Blue                  Green
  6.     Orange/White              Yellow
  7.     White/Brown                Brown
  8.     Brown/White                White (or Grey)
T568A.jpg (7305 bytes)  NOTE: This is an RJ-45 wall plate (front view), T568A.

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USOC wiring diagram

The USOC wiring is used when is most home and office telephone systems.  It used either an RJ-11 plug (4 wire) or an RJ-14 plug (6 wire).  

For telephone systems the RJ-11 (or RJ-14) wiring is reversed.  For most computer systems it is straight through.

PIN #    COLOR                    SCREW TYPE PLATE    USED

  1.     Green/White            White                    RJ-14
  2.     White/Orange          Black                     RJ-11 & RJ-14
  3.     Blue/White              Red                       RJ-11 & RJ-14
  4.     White/Blue              Green                    RJ-11 & RJ-14
  5.     Orange/White          Yellow                   RJ-11 & RJ-14
  6.     White/Green            Blue                      RJ-14

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DSL (Digital Subscriber Line)

Is growing very fast and replacing 56k modems as the price comes down.  As of this month, you can get it for $39.95 per month with a free modem.  It is many times faster than a 56k modem for downloads.

Wiring up a DSL line is easy.  It uses the same wires that you telephone line uses.

For a RJ-11 connector:

Pin #    COLOR CODE    OLD STYLE COLOR

3            Blue/White        Red

4            White/Blue        Green

For an RJ-45 connector:

Pin #    COLOR CODE    OLD STYLE COLOR

 4            Blue/White        Red

 5            White/Blue        Green

A DSL modem is installed to your telephone line, then a CATEGORY 5 RJ-45 basic patch cord is connected from the modem to a Network Interface Card (NIC) in your computer.  If more than one computer will be using the line, a hub or a bridge/router can be used to connect multiple PC's.

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ISDN circuit wiring (Integral Services Digital Network)

Two independent telephone lines are supplied on a single twisted pair cable, each capable of carrying up to 64kbs.  They are bondable together to create a 128kbs line.  A special ISDN modem is required.

The color code of the wires are the same as for a DSL line (see DSL).

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T1 circuit wiring

T1 is a high speed digital network (mainly used for businesses) which has speeds of 1.544Mbps.  Twenty four voice circuits (or channels) are available on each T1 circuit.

The T1 circuit is installed by the telephone company at the customer's DEMARK or MPOE (Minimum Point of Entry).  From there it is usually the customer's responsibility to connect to the equipment.  If you are extending the DEMARK more than 15 feet, you should follow the following:

The following is a wiring diagram for the 8 position jack.  Make sure you use a CATEGORY 5 rated RJ-45 jack.

DESCRIPTION PIN # COLOR
Receive from Network (ring) 1 Blue/White
Receive from Network (tip) 2 White/Blue
Transmit from Network (ring) 4 Orange/White
Transmit from Network (tip) 5 White/Orange
Be advised that it is possible that the telephone technician may reverse transmit and receive.  It you do not get a link, then try reversing them. 

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Copyright 2000, 2001 by L. A. Cable  -  All rights reserved.
Last Modified: Wednesday, December 19, 2001