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Making Your Own Ethernet Cables

10Base-T, 100base-T, 1000Base-T and 10GBASE-T - Making Your Own Ethernet Cables

Making 10BaseT, 100BaseT or even 1000baseT cables is easy -- uhh, well, uhmm not that hard. First, let’s get some of the basics covered so you can wire up your LAN.

CAT5 Wire

To make cables you need to have CAT5 wire. Better yet get CAT5E (CAT5 enhanced) cable so you can take advantage of NICs (Network Interface Cards) that do gigabit. CAT6a is better - might help with longer runs - but beware it has to be just so to get the promised performance.


CAT5 wire is telephone wire, so we get to learn a bit about telephone cables. No, twisted-pairs really isn't about perverts, its about noise reductions. Good telephone IW (Internal Wiring) uses real telephone cables with twisted-pairs of wire or two wires that slowly wrap around each other. Twisted pairs are used because both wires are pretty much exposed to the same magnetic field as they revolve each other so that any electro magnetic interference cancels out.

If we used two parallel wires to connect a phone circuit it would pick up so much 60-cycle hum as to be close to unusable. (You might have experienced this by using silver-satin, the common cable used to connect a phone to the wall outlet. These wires run parallel and will pick up hum if run for any distance over 6 feet.

Secret tip: Many houses have phones wired using non-twisted pairs which will reduce your MODEM connect speed! Replacing the wire from your service entrance with real twisted-pair phone wire will help you get those faster connect speeds with a 56K MODEM.) Likewise, 10/100Base-T wiring also won’t work unless you have twisted pairs.

Telco color Cable color codes

Back to CAT5 telephone cable. Phone circuits have two wires – tip and ring. (These terms refer to the old phone plugs that point was called the tip and the hole of the jack it plugged into formed the ring). The twisted pairs have color codes where one wire is of a color X (primary color) with a color Y (secondary color) stripe, and the other wire is color Y with a color X stripe. The first pair in a phone cable is White/blue (white with a blue stripe) or tip and Blue/White (that is blue with a white stripe) or ring.

TELCO Cable Wire Code


(if mostly this
color it is the tip)
next is the RJ21X
pin number
(if mostly this color
it is the ring)
next is the RJ21X
pin number
1 1 White 26 Blue 1
2 1 White 27 Orange 2
3 1 White 28 Green 3
4 1 White 29 Brown 4
5 1 White 30 Slate 5

6 2 Red 31 Blue 6
7 2 Red 32 Orange 7
8 2 Red 33 Green 8
9 2 Red 34 Brown 9
10 2 Red 35 Slate 10

11 3 Black 36 Blue 11
12 3 Black 37 Orange 12
13 3 Black 38 Green 13
14 3 Black 39 Brown 14
15 3 Black 40 Slate 15

16 4 Yellow 41 Blue 16
17 4 Yellow 42 Orange 17
18 4 Yellow 43 Green 18
19 4 Yellow 44 Brown 19
20 4 Yellow 45 Slate 20

21 5 Violet 46 Blue 21
22 5 Violet 47 Orange 22
23 5 Violet 48 Green 23
24 5 Violet 49 Brown 24
25 5 Violet 50 Slate 25

There are some mnemonics to help remember the pair order. The most common ones are: Why Run Backwards, You'll Vomit(primary colors) and Bell Operators Give Better Service(secondary colors.)

Pair Color Abbreviations

White with blue can be listed as WH/BL and blue with white becomes BL/WH. Thus pair one is made up of WH/BL and BL/WH.

More than 25 pairs

For 25+ pair cable there are more than one of every color combination. To keep them straight, the first 25 pairs are bundled together with a WH/BL yarn or plastic string wrapped around them. The next 25 pairs have a white/orange and so on until we get to 25 bundles of 25 pairs (a total of 625 pairs). Going to the next level, there are super bundles, made of 25 bundles with a white/blue string around it – this could go on to 25 super bundles of 25 bundles of 25 pairs or 15,625 pairs! You won’t see any real cables with more than 3600 pairs. The pairs are twisted and the group of pairs also twists in a slight clockwise rotation. (often you will see TELCO cables terminated at 66-blocks or 110 blocks)

10Base-T and 100Base-T cables


Now that you know more about telephone cables than you really wanted, let’s look at a standard 10BaseT cable. The ends of a cable have RJ-45 connectors. Looking at the connector with the spring clip to the back and the cable hanging down the pins are numbered left to right, one through eight. Normally, computers plug into hubs and we use a straight-thru cable where pin one of one end connects to pin one of the other end.

What is interesting is that pair-one is in the middle. This is not used for data in the current setup and is sometimes used for voice. Pair 4 is also not used and is sometimes used for power to a to a telephone set.

Straight-through Cable – both ends Based on AT&T 258A
Pin# 1 2 3 4 5 6 7 8
Wire color
Wire color
Pair 2 tip 2 ring 3 tip 1 ring 1 tip 3 ring 4 tip 4 ring

What is really insane is that analog phones are about to die - so why muddy up the standard? Or if they were going to muddy things why not stop splitting the line 2 pair to reduce cross talk? They swapped the Green and orange pair - nothing else! (So now we need a tester that can detect the color of the insulation in the cable<grin>???) The actual reason for the change is that the second pair (just outside the middle pair) was on the #3 color of the telco color standard. REALLY!  In making the move from B to A we have taken the approach of using only female connectors with 110 punch downs for new cables and use CAT6A so when 10Gbase-t becomes common the infrastructure will be ready. Bungling up standards is a crime against humanity.

The nuts and bolts of putting wires to connector

Strip the end of the cable sheath off and separate the pairs. Now take a twist or so out of the pairs being sure not to confuse the whites; some cables don’t put any stripes on the white or have a long distance between the stripes. Straighten the curl out of the wires and put them in order as the chart above. Trim the ends so they stick out of the cable about ½”. Check to make sure that the wires are still in the correct order and slide them into the connector.

Now, check and make sure that ALL the wires are all the way down to the very end of the connector (look from the end). Check once more that the wires are in the correct order and crimp. Check one last time to make sure the wires are all the way to the end of the connector and in the correct order.

Crimp with a professional crimping tool, such as AMP’s 2-231652-0. This tool has interchangeable heads for crimping RJ-45, RJ-11 and RJ-41. Don’t try to use a cheap tool – it might cause intermittent problems that will cost you much more in time that the right tool costs.

Trust but verify

Before plugging the system together it is a good idea to test the cables with a tester.

Cable length

Cable length should not exceed 100 meters (328 feet). This distance can be extended with a repeater or hub in the middle.

Crossed cables

There is also a crossed cable, for connecting two computers together without a hub, or hubs that don't have the extra jack. Pairs 2 and three are exchanged at one end.

For one end use the table above but for the other use the following table table.

Crossed Cable – Second End Only
Pin# 1 2 3 4 5 6 7 8
Pair 3 tip 3 ring 2 tip 1 ring 1 tip 2 ring 4 tip 4 ring

USOC (Universal Service Order Code) -- RJ codes


Telephone jacks have this familiar, yet poorly understood nomenclature. AMP, who sells most of theses connectors, has failed to include the RJ numbers as reference in their catalog. Because they don't have a clue as to how to organize their products , I've added the common part numbers below.

  1. Prefix
    1. RJ - prefix denotes registered jack
  2. Suffixes
    1. -C flush or surface mount jack
    2. -W wall mount jack
    3. -X - complex multi-line or series type jack
  3. Notation in tables below
    1. NC = no connection - and usually no contact
    2. T1 = Tip of line 1 -- T2 would be tip of line 2 etc.
    3. R1= Ring of line 1 etc.
    4. MB and Mb1 much the same as A and A1 - often used for data in key sets
    5. A and A1 - contacts used in old key equipment to put calls on hold



RJ11 is a standard six position modular jack or plug (whose size can have up to six contacts), but only the center two are used for the RJ11. This is your common everyday telephones jack. AMP 5-641335-3 plug AMP555163-1 jack

Pin number 1 2 3 4 5 6


JACK diagrams

Think of the pictures below as if you are looking at the phone jack in the wall. That is you are looking into the opening of the Jack as if you are ready to put the plug in. Teljack6.gif


RJ12 is a 6-position jack which is often used for one line of a key telephone system. Same connectors as RJ11.

Pin number 1 2 3 4 5 6

NC A R1 T1 A1 NC

When a phone goes off hook, the tip/ring loop closes and the A/A1 circuit closes, both through the hook switch contacts. When the telephone user wishes to put the call on hold, he pushes the 'hold' button which OPENS the A/A1 circuit. In other words, 'hold' intention is signaled by opening the A/A1 circuit while there is tip/ring loop current present. Then as the caller releases the 'hold' button, it pops up the line button. The tip/ring loop is now open, but the call is held by the KSU. When the call is picked up from hold, tip and ring are re-established, and the A/A1 circuit is closed, which actually releases the hold. Timing is critical. If the A/A1 hook-switch contacts open BEFORE the tip/ring contacts, the call will go on hold when the receiver is hung up. This is why you will find that the A/A1 contacts always establish before the tip/ring on both the hook-switch and on the line keys.


RJ13 is used in key phone systems, similar to the RJ12 but on other side of key equipment?? Same connectors as RJ11.


RJ14 is your standard two line phone - note the reversing of Tip and ring. Same connectors as RJ11.

Pin number 1 2 3 4 5 6

NC T2 R1 T1 R2 NC


RJ15 is a single Line Tip and Ring on 3-position weatherproof jack, used for providing service to boats in marinas. 1 R 2 3 T - this is not a Modular plug - it is round and has a center pin and two blades. I think it is made by Marinco.

Pin number 1 2 3

R1 NC T1


RJ17 is a 6-position jack wired with two conductors on pins 1/6 for use with medical equipment. anyone with info should post it here AMP 5-631337-3 plug 520250-3 jack


RJ18 is a single line bridged tip and ring with MB/MB1 leads. AMP 5-631337-3 plug 520250-3 jack

Pin number 1 2 3 4 5 6



RJ19 is "T/R on 4/3, A/A1 on 2/5, MB/MB1 (make busy) on 1/6" Probably obsolete interconnection for a special phone and a data set. Pin-outs would seem to be the union of RJ12 and RJ18. AMP 5-631337-3 plug 520250-3 jack

Pin number 1 2 3 4 5 6

MB A R1 T1 A1 MB!


RJ21X is another name for the Amphenol 25-pair connector (Centronics connector?) up to 25 T/R lines on a 50 pin Amphenol micro-ribbon connector, usually associated with a "66" type punch-down block. NOTE the RJ21x is the Amphenol connector NOT the 66 block. [#Amphenol see this table for pin-out]


RJ2MB is a bridged multiple-line 50-position T/R with make-busy arrangement (or the digital data on a key set phone) . The connector is the same Amphenol 50-position miniature ribbon jack as RJ21X. Every second pair is assigned to the MB. MB1 of that phone line.


RJ22 is the standard four conductor modular jack that connects a telephone handset to its base unit. AMP5-641334-3 plug AMP520249-2 Jack


RJ25 is a 6-position jack wired with all six conductors. Designed for use with three-line phones. AMP 5-631337-3 plug 520250-3 jack

Pin number 1 2 3 4 5 6

R3 T2 R1 T1 R2 T3


RJ26X is a single or multiple bridged tip and ring for programmed or fixed-loss-loop equipment. The mechanical connector is the same as RJ21X, Amphenol 50-position miniature ribbon jack and provides up to 8 lines.


Fixed Loss loop
to programming
line T R T (PR) R (PC) T R
1 26 1 28 3 27 2
.. .. .. ... ... ...
8 27 22 49 24 48 23


RJ27X is a single or multiple line bridged tip and ring for programmed (P) types of data equipment. The mechanical connector is the same as RJ21X, and provides up to 8 lines. Wiring is the same as RJ26X, except that the FLL T/R pins are left unused.


RJ31X is the jack used to intercept phone wiring for alarm systems Pins 4 and 5 connect to the line, 1 and 8 to other phones. The alarm dialer can seize the line even when it is in use. The jack has shorting bars from 1 to 4 and 5 to 8 that pass the line straight through when the dialer is unplugged.

Pin number 1 2 3 4 5 6 7 8



RJ38 is the same as RJ-31, jack has connection between 2 and 7 to indicate that the plug is inserted

Pin number 1 2 3 4 5 6 7 8

T2 A NC T1 R1 NC A1 R2




RJ45 is a standard eight conductor modular jack or plug that uses two to eight conductors. Replacing RJ11 for use with data communications and increasing use with telephones. The wire may be twisted or flat though flat will only work up to 19.2 Kbps for RS232.


RJ41S is for use with RJ25X - some ATT modems AMP5-554739-3 plug 555166-1 jack

Pin number 1 2 3 4 5 6 7 8



RJ45S isfor use with RJ25X Same as RJ41S but without the FLL AMP5-554739-3 plug 555166-1 jack

Pin number 1 2 3 4 5 6 7 8


Pin number 1 2 3 4 5 6 7 8



RJ48 is a 8-position jack wired with four conductors on 1/2/4/5, often used for T-1 networking connections

Pin number 1 2 3 4 5 6 7 8



RJ48S is a 8-position keyed jack wired with four conductors on 1/2/7/8, often used for T-1.

Pin number 1 2 3 4 5 6 7 8



RJ48X is a 8-position jack wired with four conductors on 1/2/4/5, with a shorting bar that allows a signal to pass from one pair to the other when a plug is not inserted in the jack.


RJ61X is a 8-position jack wired with all eight conductors. It is used exclusively for multiline telephone connectivity. Ethernet would use TIA-568A/B (see below)

Straight-through Cable – both ends
Pin# 1 2 3 4 5 6 7 8
Pair T4 T3 T2 R1 T1 R2 R3 R4


Sometimes called T568A. A common arrangement for networking that uses an 8-position jack wired with all eight conductors, standardized by the Electronics Industry Association and Telecommunications Industry Association. Pairs 1 and 2 are on pins 4/5 and 3/6, respectively, and as such allow for backwards-compatibility with older USOC jacks. However, as pairs 3 and 4 are on pins 1/2 and 7/8, respectively, the entire jack is not USOC-compatible. It is sometimes used for 10-Base-T wiring, but is more suited for Type-3 Token Ring.


Also called T568B and by AT&T's 258A spec. The most common wiring scheme for 10-Base-T and 100-Base-T networking today. It specifies an 8-position jack with all eight conductors wired; however pairs 1 through 4 are on pins 4/5, 1/2, 3/6, and 7/8, respectively. The only difference between T568B and T568A is the arrangement of wire pairs. A patch cable of either type will work on the other (wire pairs will simply be different colors). Be cautioned, however, that jacks wired for one type will not be compatible with equipment wired for the other.

There are some mnemonics for EIA/TIA568B:
"Bad Officer WearinG Blue Wide Belt Go Bully"

Bad - type B EIA/TIA568
Officer - Orange
WearinG - White Green
Blue - Blue
Wide Belt - White Blue
Go - Green
Bully - Brown

IEEE 10-Base-T

Just a T568B pattern with the unnecessary pairs removed, leaving only pairs 1/2 and 3/6 wired.


Digital Equipment Co.'s proprietary Modified Modular Jack. It is identical to a standard USOC 6-position jack, except that the locking tab has been offset to the right to prevent an MMP (modified modular plug) from fitting into a USOC jack. AMP5-555237-2 Plug

AMP part # for modular plugs and PCB sockets

Realize that there are three connectors housings. (four if you count DECs)

  1. RJ22 or hand set connector. it has four positions and 2 or 4 contacts
  2. RJ11 type or your standard phone plug -- it has 6 positions with 2, 4 or 6 contacts.
  3. DEC type RJ11 with offset latch 6 positions with 6 contacts.
  4. RJ45 type - it has 10 positions (yep, you can get 10) and 8 or 10 contacts
USOC type Positions Contacts AMP Plug# AMP Jack # *AMP Die #
RJ22 4 4 5-641334-3 520249-2 853400-3
RJ11 6 4 5-641335-3 555163-2 853400-8

6 6 5-641337-3 555163-1 853400-8
DEC RJ11 offset 6 6 5-555237-2 555003-1 853400-6
RJ45 10 8 5-554739-3 555162-1 853400-7

10 10 5-557963-3 558065-1 58560-2*

All other dies use the 2-231652-0 crimper

RS232 DB9 pinout and null modem wiring.


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