Visit our newest sister site!
Hundreds of free aircraft flight manuals
Civilian • Historical • Military • Declassified • FREE!


TUCoPS :: Phreaking Technical System Info :: cables.txt

Telephone Cabling colour scheme




 ***************************************************************************
 *                                                                         *
 *                           The Telephone Works                           *
 *                              Egghead Dude                               *
 *  CHiNA                                                           CHiNA  *
 ***************************************************************************

         Welcome to CHiNA Educational InfoFile Series II, # 3.  Once again,
    be looking for new files weekly for the next few weeks until school starts
    again.  And contrary to Megaton Man's belief, we are still very much alive
    and in production.  If he tells you otherwise, kindly call him a peasant
    and tell him to fuck himself...if you want.  Enjoy!


Here are the standards in Telephone Color Coding:

         Telephone circuits are paired as 'tip' and 'ring' wires. On POTS
    (plain old telephone service) tip is 0 volts and ring is -48 volts (tip is
    not 'ground' though as it is a blanced line).  The pairs must be
    distinguishable from one another easily so they are colour coded.  The
    colour of the wire indicates whether it is tip or ring.  In a quad wire
    green and black are tip while red and yellow are ring.

         pair#          tip colour          ring colour
         _____          __________          ___________

          1             white               blue
          2             white               orange
          3             white               green
          4             white               brown
          5             white               slate  (silver)
          6             red                 blue
          7             red                 orange
          8             red                 green
          9             red                 brown
          10            red                 slate
          11            black               blue
          12            black               orange
          13            black               green
          14            black               brown
          15            black               slate
          16            yellow              blue
          17            yellow              orange
          18            yellow              green
          19            yellow              brown
          20            yellow              slate
          21            violet  (purple)    blue
          22            violet              orange
          23            violet              green
          24            violet              brown
          25            violet              slate

         An individual wire is identified by it's colour and the colour of
    it's stripe.  The main colour determines whether it is tip or ring while
    the stripe identifies it's pair (i.e. a black wire with a blue stripe is
    tip of pair 11).  In many cables the stripe is missing in which case the
    pairs are distinguished by the way they are twisted, by pulling back the
    sheath pairs are more obvious.

          As you can see there are only 5 tip colors and 5 ring colours (5
    x 5 = 25). a 100 pair cable is made up of four of these 25 pair bundles.
    The first bundle is wrapped by a white/blue binder string, the second by a
    white/orange binder, the third by a white/green and the fourth by a
    white/brown.  This scheme can be extended infinitum.

         Some folks think that the order is:
     Pair  Tip  Ring
       1   RED   GRN
       2   YEL   BLK
       3   BLU   WHT,
    and that the 1st pair was backwards in a modular connector compared to the
    rest.

         Wrong. The polarity is off.  Modular connectors reverse the polarity
    so they make the issue pretty confusing.  A modular line cord (that is a
    properly made _telephone_ line cord) has a flat topology such that when
    laid on a table the top of both connectors is up.  This means that a
    reversal (polarity wise) takes place.  Tip becomes ring on all pairs (the
    wire is a ribbon in theory). the top of both connectors is up.  A 'set'
    jack (the one inside the telephone) is wired backwards to compensate.

         In addition, the system employed throughout the (used-to-be) Bell
    System was actually very simple. There wer five colors assigned to "tip"
    and five colors assigned to "ring". This gives a total combination of
    twenty-five pairs (very convenient!).

         The colors assigned to the "tip" are;

     white   wt
     red     rd
     black   bk
     yellow  yl
     violet  vi

         The colors assigned to the "ring" are;

     blue    bl
     orange  or
     green   gr
     brown   br
     slate   sl (sometimes mistakenly called gray)

         Standard phone convention is to identify the "tip" first and then the
    "ring" when referring to a pair. Thus, the first five pairs of a telephone
    cable are the "white" pairs;

     white/blue   wt/bl
     white/orange wt/or
     white/green  wt/gr
     white/brown  wt/bn
     white/slate  wt/sl

         The next five are the "red" pairs:

     red/blue     rd/bl
     red/orange   rd/or
     red/green    rd/gr
     red/brown    rd/bn
     red/slate    rd/sl

         And so on, until all twenty five pairs are identified. What happens
    when there are more than twenty-five pairs in a cable? Simple, enclose
    each twenty-five pair group in a color coded binder. And guess what the
    color coding is for the binder. Yep, the same as the wires in the binder.
    The first binder group is the "white/blue" binder the second is the
    "white/orange" binder, and so on.  If it is necessary to refer to the
    twenty-sixth pair of a fifty pair cable it is referred to as "two
    white/blue" or 2-wt/bl. The seventy-ninth pair in a one-hundred pair cable
    is called "four white/brown" or 4-wt/bn. This all holds true for the first
    twenty-four binders in a cable.  The twenty-fifth binder is a little
    different, and my recollection is a little hazy but I believe the binder
    colors are white-white-blue. Yes that's two whites and a blue. It might be
    two blues and a white.  It's been a long time since I was in a cable over
    six hundred pairs. One thing I know for sure is that they double up on one
    of the binder colors after the twenty-fourth binder group.

         There is also a convention for the positioning the pairs on
    connecting blocks.  The Ring is usually on the Right and the Tip is
    usually on the Top.  As you can see there is a pattern here, Ring-Red-
    Right and Tip-Top.  I guess this was done to make it easier for us dumb
    installers to remember! |-)

         The only difference in the color coding between telephone cable (the
    stuff used outside and strung along poles or underground in conduit) and
    telephone inside wiring (the gray colored stuff in the walls and up in the
    ceiling) is that the inside wire has each pair traced with the color of
    its mate.  That is, the first pair is a white wire with a blue tracer and
    its mate is blue with a white tracer.  This is done to avoid "splitting" a
    pair.  Splitting is getting the ring of one pair and the tip of another.
    In outside phone cable each pair is twisted with its mate and the chances
    of splitting a pair are not as great (although it's been known to happen
    ;-)).

         With wiring done inside a house, a little history is in order. Back
    when we had party-lines,(I know, we still do, but very few still in
    service and none available for new service) three wires were necessary
    because a ground was required to make the bell ring.  So, the original
    phone wiring had three conductors, red, green and yellow.  Red and green
    were ring and tip respectively and yellow was the ground.  Then people
    started getting away from party lines and into princess and trimline
    phones with lights in the dial.  The yellow was no longer the ground and a
    black wire was added and the yellow and black were used to supply power
    for the lamps from a small transformer.  Time marches on, and now people
    are getting second lines installed in their homes. Since the new phones
    get the power for their lamps from the phone line directly, the yellow
    and black are now "spare".  The yellow is usually the ring and black is
    the tip.  Of course, houses that have been pre-wired with six-pair inside
    wire would normally have line 1 on the white/blue pair and line 2 on the
    white/orange pair.  In many pre-wire installations I have found that the
    sixth pair (red/blue) was used for transformer power, although I don't
    believe that was ever an official practice.

            Written by: Egghead Dude        Edited by: The Conflict
                        Golf City BBS
                        CHiNA Node #5

         Hope you enjoyed this one, and once again, look for more!  Please
    distribute this file freely, and if you really must speak to CHiNA,
    contact us on one of our member boards (a node list should be available
    wherever you receieved this file).  Thanks for you support!

         A big HELLO to Mr. X, The Maestro, Barimor (hear you're doing wonders
    for the FiRM!), Jolly Green Giant, Feetsack, Lord Blix, Maxwell Smart, The
    Viper, etc...if you want to be said HELLO to, too bad, we don't like you!
    Really...we'll be seeing you!



TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2014 AOH