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