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#442517 04/20/05 09:55 AM
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OK, folks. It's slow in here today and I have been thinking about this issue for a very long time. In the telecommunications business, we have our practices frequently dictated by architects and IT personnel who have absoultely NO concept of what the term "RJ" actually means.

Now I will get upon my soap box. RJ was a national standard that was created so that a customer with a piece of FCC registered equipment could contact any local telephone company, anywhere in the US, give them the RJ requirement (Registered Jack) indicated on the device and the installer would know exactly how the jack needed to be wired. It had absolutely nothing to do with the size, brand or model of the jack itself; it was how the pins were wired when connecting to the public network (PSTN).

Today, you frequently hear "RJ45" as the description of an 8-wire (4-pair) jack. RJ45 was a single telephone line appearing on pins 4 and 5 of an 8-position jack. Pins 7 and 8 were shorted with a resistor that was sized to "tell" the modem connected to the jack the level of line loss that was determined by the installer. Computer room guys back in the '70's and '80's picked up on the buzz word RJ45 because it made them sound as if they actually knew something about this subject. I mean, the plug and jack look different, Bell installed an RJ45, so the 8-pin plug must simply be and RJ45. The rest is history.

What really kills me is the variations of 4 pin, 6 position plugs and jacks. I am sure we all know the basic RJ11, where the telco line was connected to pins 3 and 4 of a standard 6 position jack. All other pins were simply not used. Then there came the RJ12, where the RJ11 was wired to accommodate a pair of 1A2 "A" leads on pins 2 and 5. RJ13 was a variation of this, RJ14 was an RJ11 with a second telco line connected to pins 2 and 5. RJ17, etc. never were big items, but still the RJ25 existed for a while. This was a three line jack; an RJ14 plus a third line on pins 1 and 6.

Then lastly, the ever-popular RJ21X. A 66 block with a female 25 pair Amphenol connector on the lower right side of the block. It was a mass demarcation point where the telelphone company provided up to 25 one-pair lines. There were other RJ variations usinig this same type of block, but the pros out there know what I am talking about.

Today, look in any datacom catalog (not one from a reputable telecom supplier) and look at their product descriptions:

2 pair modular plugs = RJ11
3 pair modular plugs = RJ12
4 pair modular plugs = RJ45

And the ever-popular:

25 pair cables, regardless of length, type or connector gender = RJ21X

Nowhere in my days have I ever seen an industry's standardization so grossly butchered by outsiders. I try to correct IT guys all the time that what they really want is a cable run and jack conforming to the EIA/TIA 568A/B wiring standard, not an RJ45. I have even gotten sadistic and given them a real RJ45 wired connection! I then refer them to the wiring pinout diagrams in any Suttle, Siemon or Leviton catalog. It shuts them up, but do you really think they listen or better yet, comprehend?

OK. I will come down from my soap box now. I thank you for your time and input!

------------------
Ed
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How come there's always enough time to go back and fix it a second time?


Ed Vaughn, MBSWWYPBX
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#442518 04/20/05 10:24 AM
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I'm sure that is with any business, people call things that they are not. You yourself called a 25 pair connector an "Amphenol connector" when in fact Amphenol is a manufacturer of electrical and electronic equipment. 3M, Amp, TRW, and several other companies make the 25 pair connectors.
Another example would be inline skates, people often refer to them as rollerblades, rollerblades is a company that makes inline skates.

#442519 04/20/05 10:31 AM
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Brilliant observation!!!! As I reviewed my post (and even went back and edited it), I thought about that terminology since it was a name-brand. That pretty-much countered half of what I stated! I just figured that that was the most easily-recognized name for a 25 pair connector. Yikes! I am falling into the IT trap! Thanks for keeping an eye on us old-timers.

------------------
Ed
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How come there's always enough time to go back and fix it a second time?


Ed Vaughn, MBSWWYPBX
#442520 04/20/05 12:53 PM
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Ed, BRAVO! Fifteen years ago I had this same discussion with a rocket scientist at NASA at Edwards AFB. They wanted an RJ45 on the end of a "computer" wire. It seems after only 6 years of college education in the technology of computers HE STILL DIDN'T know that he didn't know.
After involving the chief of engineering the issue was resolved --- the IT types would tell us what they wanted to accomplish and we "Wire Monkies" would install the proper hardware. The brain boys always had a hard time even telling us what they wanted. They could tell you all you wanted to know about the thermal dynamics of rentry but couldn't dial a phone.

OOOPS, I'd better get off your soap box. Tanx for the chance.
KLD


Ken
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#442521 04/20/05 02:20 PM
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That's one reason I switched from IT to phones. Too many idiots that say they need more memory when they really need a bigger hard drive, calling a 3.5" floppy disk a hard disk, putting CD's into 5.25" floppy drives, ...

Oops, someone please kick me off the soap box.


Joe
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No trees were harmed as a result of this posting; however, many electrons were severely inconvenienced.
#442522 04/20/05 06:20 PM
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Back in the old MA Bell monopoly days it was all Universal Service Order Code (USOC). Then Carterphone said "Let My People Connect". All the USOC jacks with detailed sketches were added to the FCC regs. Today they are gone from the FCC regs and administered by a privet telco assocation.

#442523 04/30/05 03:35 PM
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Wow. Awesome post! It's so hard to get this info in the field, because I get the feeling that no one around here really knows what they're talking about.

Here's a question for you. When I'm shopping modular plugs, they're labeled "6 position RJ-11". Since there's obviously no wire yet connected to the plug, is it acceptable terminology to refer to them as RJ-11, or is there a more suitable name?

#442524 05/02/05 02:47 AM
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Well, as you can tell by my original post, I tend to put way too much thought into a dying part of our industry's orginial standard.

Just for the record, there are generally only two types of modular plugs and jacks. The six position, commonly referred to as RJ11, and the eight position, commonly referred to as RJ45.

The six position can be wired with two wires on pins 3/4, therefore an RJ11. This same plug can be wired with four wires on pins 3/4 and 2/5, thus becoming an RJ12, 13 or 14. Finally, this same plug can be wired with three pairs on pins 3/4, 2/5 and 1/6 to become an RJ25 wiring configruation. So, as you can see, it's not the actual plug that determines the "RJ" number, it's how that same plug is wired for the different configurations.
So, to answer your original question, yes, it's OK to refer to a 6 position plug or jack as an RJ11 because it's how you wire it that determines the true RJ configuration. Play it safe and buy 6-position plugs and jacks and you can't go wrong.

This program was originally developed as "USOC" (Universal Service Order Code) by the FCC so that all telephone companies in the United States were on the same page when a customer called requiring a jack installation. Whether it was GTE or Michigan Bell, an RJ11, RJ14, etc. was the same to all operating companies.

By all means, the most common RJ configurations you will see today is the RJ11 (one line on a 6-position jack) and RJ14 (two lines on a 6-position jack).

You won't see an RJ45 being installed anymore since it dealt largely with telephone company-owned modems or very high end ones provided by the customer. It was an 8-position jack wired with a single phone line wired to pins 4/5. A resistor was connected across pins 7/8 by the telephone company installer who measured the line's loss and this resistor told the modem to adjust it's transmit/receive levels accordingly.

Today's RJ45 is just a misnomer for an 8-position jack/plug used for data network wiring. Today, usually all 8 positions are wired with four pairs of wire, regardless of category 5,5e or 6. It's a far cry from the original RJ45, but since the jack remains pretty much the same with regard to physical shape and appearance, it got it's name that way.

------------------
Ed
---------
How come there's always enough time to go back and fix it a second time?

[This message has been edited by ev607797 (edited May 02, 2005).]

[This message has been edited by ev607797 (edited May 02, 2005).]


Ed Vaughn, MBSWWYPBX
#442525 05/02/05 09:42 AM
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Nice. I will from this point onward be referring to my network jacks by 568A or 568B [Linked Image from sundance-communications.com]

#442526 05/02/05 04:26 PM
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Wasn't the USOC code for a mod plug "266"?
That was for the line cords --- but ---fuzzy memory ---- 264 for the handset cord?

But I don't smoke cigars. GS. [Linked Image from sundance-communications.com]


Ken
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