"The phone is a remarkably complex, simple device,
and very rarely ever needs repairs, once you fix them." - Dan/Panther

Main Menu

RJ-11, RJ-14, and RJ-25 Modular Jack Wiring

Started by unbeldi, May 16, 2016, 11:30:06 AM

Previous topic - Next topic


Since the 1970s, most telephone connections in residences and offices use modular miniature jacks and plugs, having two, four, or six conductors.

Modular connectors are correctly described by the number of pin positions, and the number of pins actually installed.  The standard telephone connector has the width of six pin positions, while only two or four are most commonly filled with contacts.  Thus, they are called 6P2C, 6P4C, or 6P6C connectors, with P = position, and C=contact.

Correspondingly, they accommodate connection for one, two, or three telephone lines or wire pairs.

Despite the correct nomenclature, these jacks and plugs are often called RJ-plugs and jacks. RJ is always followed by some number.  Great confusion exists about these numbering schemes, and sadly even major parts distributors label them incorrectly. One can find all kinds of wrong numbers, some of which never existed in any official documentation.

Registered Jacks were created in the 1970s by AT&T/Bell System in cooperation with the Federal Communication Commission (FCC) in the US to facilitate simple, modular connection of authorized (registered) third-party equipment to the telephone network, in the name of open competition between vendors, and consumer choice.

According to the FCC Registration program, circa 25 different Registered Jack types were defined.

A Registered Jack is not only a connector type, but primarily an interface specification that includes the purpose and type of electric signals transmitted.

*RJ11 uses a 6P2C jack and plug for one telephone line, which uses the two center pins.  A second pair may be used for powering a night lamp, or other circuitry, in which case the RJ-11 uses a 6P4C connector.

*RJ14 is used for two telephone lines. When only the lines are wired, it uses a 6P4C connector, with power a 6P6C connector is used.

*RJ25 is the interface for three telephone lines. It uses all six pins of a 6P6C connector.

The pin assignments and standard color designations for these, the most commonly used modular Registered Jack (RJ) types are shown in this diagram.

The diagram is drawn for looking straight into the female jack. The metal contacts are at the top. The plastic locking tab is on the bottom.  The left-most contact is number 1.

Wiring cords used with modular plugs use primarily two color schemes. The older Bell System scheme uses solid colors only (bottom set), while the newer schemes adopted from the 25-pair telco cabling system use a two color scheme, in which one color is the dominant base color, and the second is usually a thin stripe on top. A wire pair simply exchanges the base and stripe color for its two conductors.

==BSP references==
*BSP 463-400-120 i1 7805--Registration Interface; Bridged Single Line TIP and RING Arrangements; RJ11C, RJ11W, RJ12C, RJ12W, RJ13C, and RJ13W
*BSP 463-400-140 i1 7805--Registration Interface; Bridged Two Line TIP and RING Arrangements; RJ14C and RJ14W
*BSP 463-400-142 i1 7910--Registration Interface; Bridged Three Line TIP and RING Arrangements; RJ25C


I mentioned confusion about RJ-type connectors in the first post.

Another modular connector type is the 4P4C connector.  This was originally used for connecting a handset to a modular telephone set, but since has found usages for all kinds of electrical connections to apparatus.

As the name implies, it is physically smaller than the modular connectors used for telephone line interfaces, having a width of only four positions.  It always has all four positions occupied with contacts, hence it has a 4P4C designation.
At least, I have never encountered a 4P2C.

As this type of connector is never used to connect anything to the telephone network, it has never received a Registered Jack (RJ) designation.

However, this type of connector is often incorrectly called an RJ9, and perhaps other names.  Be aware, that this is purely wrong and confusing on top.


This is interesting. Are they compatible? When I say that I mean, for instance, would the green and red contacts in a RJ11 line up with the same contacts in a RJ25?

Panasonic 308/616 Magicjack service


Quote from: Pourme on May 16, 2016, 06:16:06 PM
This is interesting. Are they compatible? When I say that I mean, for instance, would the green and red contacts in a RJ11 line up with the same contacts in a RJ25?
yes, certainly.   The color code for each pin is identical between each connector type, as shown in the diagram, it is only the number of contacts that are actually wired that is different.


how about the RJ45? how is that wired in comparison to the RJ25?


Quote from: Babybearjs on May 16, 2016, 09:22:03 PM
how about the RJ45? how is that wired in comparison to the RJ25?

RJ45 is today understood to be an 8P8C connector, so it can hardly be compared in terms of wiring.

But nevertheless, the designation has been abused just the same, as the proper original designation was RJ45S.
It was a keyed 8P2C connector for only one pair for a data line, but it had a shorting bridge on pins 7 and 8 for equipment programming.


RJ45 is today understood to be an 8P8C
Right, but here in Norway we use it for telephony too, center 2 is line wires other configurations might wary but usually this is enough.

I do not like to use the same pairs as LAN uses, so in my house you may find the 2 pairs not used for LAN connected to telephone lines, but I try to keep the old 3 pin standard, or US standard where integrated in other equipment.



the 568A version is straight through. the cable pairs are in line (Blu, Org, Grn, Bwn.) so using them for telephone usage is easy.... the 568B is a little harder.... (Blue GRN ORG Bwn) the 2nd, 3rd pair is reversed.... I use these on my system. remembering the reversal gets me at times.... I'm so used to Blu Org Grn Bwn.... that sometimes I get my A-Lead and Lamp 1 mixed up....


I needed a bunch of modular cords to test my new PBX system.  After collecting several that I had lying around I decided to make up a few more.  I started looking at my existing cords to get the correct color order and was surprised that many of the "store bought" cords were not connected the same.  So I went online to find the correct color diagrams.  After getting the correct connection diagrams online I started comparing my cords to the correct diagrams.  I figured as long as the the same color was connected to the same end I would be OK, but was surprised that this was not always the case.  After checking all of my cords visually and with a modular cord continuity tester I found that the cords divided up roughly 50/50 into two categories.  The first would have each end connected together exactly the same, i.e. looking at the RJ plug at each end of the same cord I would see the same colors in the same order on each end (for example, B-R-G-Y on one end and then B-R-G-Y on the other end).  I had always assumed that this was the correct way to attach plugs on to each end of a wire, I realized it wouldn't really matter for functionality what the color order was, as long as it was repeated exactly the same on each end. However, I discovered about half of the cords would be B-R-G-Y on one end, and then the mirror of that (Y-G-R-B) on the other end.  This won't work will it?  Doesn't it reverse the polarity one end to the next?  The fact it is mirrored won't mix up the tip/ring pairing of each line, but they will have reversed polarities, right?  If I had found one or two like this I would have assumed that they were put together wrong and threw them out, but now I am questioning myself.  Do these have another purpose? Do I have it all wrong?  I don't own any early Touch Tone phones, so maybe that is why I have never noticed any polarity issues before.  Any ideas???


With 6-position 4-contact plugs, they should be BK-R-GN-Y on one end and Y-GN-R-BK on the other. The 623-type jack in the base of the phone will reverse polarity again so that green from the wall jack goes to the green lead of the 623, which goes to L1 in a Western Electric 2500.
"C'est pas une restauration, c'est une rénovation."--François Martin.


Thanks for the info Poplar1.
I have wondered about that reversal thing too.
Question: If my phone does not have one of those reversing sockets,
then what of the reversing cables? what effect would it have on a network?


With the "modern" touch tone phones it does not matter, only on the early ones.
Harry Smith
ATCA 4434

"There is no try,
there is only
do or do not"


reversal is always a problem for me.... I take a RJ-45 cord of 25 ft, cut it in half and spade the ends....when wiring it into my phone there are time where the T and R leads are backwards in the cable... (it might be just 1 pair, but that throws a wrench into the setup all the same) the same happens with the "Keystone" jacks.... there are time when the wiring labels come off the jacks and you have to rely on memory to wire them up.... (now, which side did the green pair go on???) when I run into this, its just a matter of switching the lead positions on the terminal block in the phone...., but then.... if its the wall jack.... then the problem continues if you move the phone to another location.....


As I remember the standards, network cables shall be equal in both ends, phone cables are reversed. I do not know why.