Difference Between Similar Terms and Objects

Difference Between RJ11 and RJ12

rj452RJ11 vs RJ12

The registered jack standard has been around for some time for people to follow in wiring their telephone lines. It is abbreviated into RJ and is then followed by two digits that identify the specific standard. The RJ11 and RJ12 standards are quite closely related and in fact look identical to each other to the uninitiated. This is because they both use the same six slot connector. The only difference between these two is in how they are wired and the number of the wires that are being used.

RJ12 is a 6P6C wiring standard. This means that there are also 6 wires that are terminated in the connector, occupying all the available slots. RJ11 is a 6P4C wiring standard and only has four wires connected and the remaining two slots are no longer used. Because of this, you would need to pay close attention to the cables that you are utilizing as cable used four RJ11 might not be suitable for RJ12, even if they look identical.

Despite the differences, both wiring standards are used for the same purpose, telephone lines; commonly using the center pair. But there are also other applications that make use of the RJ12 standard. Keyed telephone systems and PBXs may take advantage of the additional two connectors. Because of this, RJ12 is not really very common and only the people who have experience working with large company’s telephone systems are familiar with RJ12 wiring. RJ11, on the other hand, is relatively very common because it is used in the majority of the phone units and wiring of some telephone companies. This has even developed into the connector itself being popularly referred to as RJ11.

There is really no individual decision whether to choose RJ11 or RJ12 in your connection as this is often dictated by the telephone company that you are subscribed to. With that said the additional two lines that are made available when using the RJ12 standard can become quite handy in a PBX system where you can add extra lines on your own.

1. RJ11 and RJ12 wiring uses the same six slot connector
2. RJ11 and RJ12 only differs in the wiring
3. RJ12 utilizes all six slots while RJ11 only uses four of the six available slots
4. RJ11 and RJ12 are commonly used for telephone systems with RJ12 being used in different configurations
5. RJ11 is very common in today’s homes while RJ12 is quite uncommon except in some large companies

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  1. Interesting, since RJ-12 and RJ-13’s have long been deleted. Both of them refer to A&A1 leads in front of or behind a key system station. Not many 1A2 key systems out there today 🙂

    The correct terms and usage is RJ-11, RJ-14 and RJ-25 for 6p 6c plugs using 1,2, or 3 pairs, and RJ-61 using 4 pairs on a 8p8c plug.

  2. I had never heard of RJ12 until “Santa Claus” got my son a Lego Mindstorms NXT 2.0 Robotics Kit. The kit uses RJ12 wiring to connect sensors to the central control unit.

  3. Unlike other cables where you have to run a cable for video and a separate cable for power, our RJ12 cable has the power, audio and video built all in one. Our simple snap in cable makes connecting the camera to the DVR as easy as plugging in a phone line

  4. Wow, I read it on the internet so it must be true. Once again, RJ-12 and RJ-13 are DELETED items in the FCC jack registration program. http://www.allentel.com/pdf/technical.pdf

    When someone refers to an RJ-12 and the 12 being this or that, it shows your ignorance.

    • Are you suggesting that there is no difference between RJ12 and RJ25 or RJ11?

      Seems like there’s a difference in wiring layout – maybe cross-over vs. straight-through?

      I know I’ve read of equipment (non-telecom) that required RJ12 standard cabling that got screwed up by using standard pre-made telephone wires. I think voltage got transmitted somewhere it wasn’t supposed to be.

      Thanks for any insight on the wiring differences between RJ11 vs RJ12! (Good article, but this question seems to contain the meat of the difference between RJ11 and RJ12 but the article doesn’t go into any detail.)


      P.S. A standard being “deleted” is a curiosity of the standard and really only applies within the world of regulated telecom – not necessarily, or even typically sometimes, a reflection of what is happening outside that realm, whether speaking of the USA or elsewhere.

      • Actually, read on in the comments. In the United States, RJ-12 and 13 mean something different and the use of that designation has become obsolete with the demise of 1A2 key telephone equipment.

        We use the 6 pin modular connector to wire 1,2 and 3 lines in an RJ-11, 12 and 25 configuration with the pinouts being 432516 for the Tip and Ring of lines 1,2 and 3. Other Countries use RJ-12 the way we use RJ-11 (Oz) and some European Countries also use the “RJ” designation.

        We get the same confusion in our 8 pin system, incorrectly referred to as RJ-45. Ours can be keyed or non-keyed, and wired for data in a T-568a,T-568b, or RJ-61 configuration. T1 and other schemes use the pins differently.


  5. It´s so nice when people are friendly to each other…
    RJ11, RJ12 and the RJ25 is widely used in Sweden.
    But for telephones??? Very uncommon cause we are only setting up unwired phones nowadays.
    Mobilephones is what we use,

    But, please, don’t say the RJ11 and 12 are deleted, they certainly are NOT!


    • Thanks. I guess I wasn’t clear. FCC is the United States Federal Communications Commission. In USOC FCC registration, RJ-12 and RJ-13 are deleted. I forgot that this might be an International forum. I remember that Australia has RJ-12’s which is the U.S. RJ-11, and clearly in your country you have thm too! http://www.ji.com.au/telecomsplugs/


  6. I currently have a video security camera set-up installed that uses RJ11 connectors from the camera to the DVR. I was hoping to replace the system,except for the cables. The new system I found uses R12 connectors. From what I have read from this forum is that these are not wired the same so therefor I should not exspect my new system to work properly and might even ruin its functionality. Not being to wise on electronics, I will wait to see some comments on this.
    Thank you

  7. I am looking through forums trying to find answer to my situation. I have a video security system. It is made in Korea and it uses RJ-12 connectors. I have pre-made 50 ft. cables, but I have one camera I want to put 200 ft. away. I purchased 250′ of CAT 3 cable which has 24/3 pair of cable. So I have 6 wires and I purchased RJ-11 6P6C plugs. So, now I need to figure out what wires go where in the plug and I figure I can watch a youtube video to learn how to crimp the plugs on the 6 wires (My crimping pliers must have assumed I new how to use them).

    So I have wire I am almost positive I can use, and the RJ-11 plugs fit my equipment and there are 3 pairs or 6 wires, I just need to know how to align them in the plug.

    • If you’re wiring both ends, it shouldn’t matter. The problem is whether you’re making voice or data cables. The splits for paired cables is 432516
      which means the white blue goes to 4 the blue white goes to 3 as you look at the plug with the pins up and the tab down. The problem is, in a telephone wire, the white blue would end up on pin 4 on one end and pin 3 on the other. So, you will have to look at the old cable to determine what wiring they used to make up the cable.

      The rest of the paired cable code is white orange to 2 and white blue to 1.

      You also have a 50-50 chance that the extension won’t work, just because of the increased distance.

  8. i need full information about rj families

  9. RJ12, 6P6C, connectors are used extensively on ham radio microphone connections.

  10. Argh..

    This article is wrong….

    RJ-11 6 pins 2 conductors
    RJ-14 6 pins 4 conductors
    RJ-12 6 pins 6 conductors

    So.. This article says RJ-11 has 4 conductors, this is simply incorrect.

  11. My 14 Yr old just got an old dial phone from the sixties. It works for incoming and outgoing when I plug it into the telephone box. However, she doesn’t have a box in her room to plug it into. I was going to get 50 ft of cord ext and hook it into the downstairs box. Then, I came across the female to female adapter I need to complete the circuit. Does it matter if I get RJ11 or RJ12?
    She’s ecstatic over this old phone. I thought most companies got rid of the old pulse lines and thought she’d only be able to receive calls but was pleased to find out she can do both.

    • These systems have been around for a long time and connect to the Public Switch Telephone Network (PSTN) over Plain Old Telephone Service (POTS) lines. The PBX manages calls between phones and fax machines by being physically connected to them over copper wiring. Incoming calls are routed through the PBX and out to the phones, and calls can be transferred between phones via the PBX. The PBX itself typically lives in an office’s telecom closet. RJ 12 STILLL EXIST ,///**:::….

  12. Fantastic website. Plenty of useful information here.
    I’m sending it to some buddies ans also sharing in delicious.
    And naturally, thanks in your sweat!

  13. Slow potentials of the cerebral cortex and behavior.

  14. Lol, this article is about RJ11 and RJ12, but the first image shows an RJ45 plug…

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