Cat5 RJ-45

tom baker

First Chief Moderator
Staff member
But they do know what other wire they are twisted with.

These are the bozos who give us a bad name. Either learn what the color code is for 568A and 568B or don't do it at all.

And, you should know that I forbid field installing RJ-45 plugs.

-Hal
I agree I have tried to field install plugs even with a Pallidin tool, that the wires go thru the plug and are trimmed off. Its hard to do. If the light is not good I get the orange and brown mixed up
 

Salama

New User
Location
Sarasota
Occupation
Engineer
I agree that the colors don't matter as long as each pair is wired as pairs.

You could use the brown/white pair on 1&2 and the blue/white pair on 3&6 if you wanted.

A crossover cable is the only kind you would intentionally mix end pairs.
Agree 100% . Cross over this is the correct term.
 

Mr. Serious

Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
He's saying you could do Orange on pin 1, orange/white on pin 2, blue on pin 3, blue/white on pin 4, green on pin 5, green/white on pin 6, brown on pin 7, and brown with white on 8 and as long as the other end is exactly the same, will be fine
I worked for a wireless ISP, and had a service call for flaky/slow internet service. The guy who had originally installed it put the ends on the cable exactly as you said. I think there had been one or more previous service calls where the tech going out there didn't notice the cable ends were wrong. The customer had always had problems, despite good line of sight to the tower and minimal interference in the area, so they sent me and the other most experienced person to figure it out.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Yep, the old RJ-31X. And countless number of them installed wrong so they did not seize the line.
In an example of belt and suspenders, we always install the RJ-31X at any site using POTS, or simulated POTS. The shaking-my-head part is that we always tell the customer they need to give us dedicated phone lines, which obviates the need for the line seizure jacks.
 

tthh

Member
Location
Denver
Occupation
Retired Engineer
If you are over 50, you gotta have a headlamp :) I keep a headlamp and drugstore magnifying glasses in my tool kit. I have a Black Diamond Spot 350 and it works good. For daily use it might be less practical since it isn't recharagable.
 

tom baker

First Chief Moderator
Staff member
But they do know what other wire they are twisted with.

These are the bozos who give us a bad name. Either learn what the color code is for 568A and 568B or don't do it at all.

And, you should know that I forbid field installing RJ-45 plugs.

-Hal
I agree. It’s very challenging to get the pairs in the connector correctly. I tried different tools, made no difference….
 

Another C10

Electrical Contractor 1987 - present
Location
Southern Cal
Occupation
Electrician NEC 2020
You will end up with split pairs. It is not just about continuity.
I always use the B configuration and considered from the above post, thinking really any color coding sequence could determine the same outcome, but you mentioned the paired twist .. makes sense somehow to this ol' wireman, how are data packets lost through the unequal pair.

just curious .. some sort of harmonic interference .. just a guess
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Each pair is meant to carry a balanced differential signal. The balanced part reduces the electric an magnetic fields in the vicinity of the pair which the expected equal capacitive coupling between any "outside" signal and the two wires of the pair allows the differential receiver to null out almost all of both cross-talk and external noise pickup.
Without that pairing, cross talk can be extreme to the point of causing data loss.
The second mechanism is that each twisted pair is a transmission line with a specific characteristic impedance. The receiver or end of line terminator matches that impedance, minimizing reflections at the end of the line. But a transmission line made up of one wire from each of two twisted pairs will have a different impedance. The resulting reflections from the improperly terminated wires allow each "pair"'s signal to interfere with itself, to a degree depending on the length of the lines involved.
 
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Mr. Serious

Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
I agree. It’s very challenging to get the pairs in the connector correctly. I tried different tools, made no difference….
I guess some people are just good at it and some aren't. I am good at it, but it does take me some time to get it done. Here's how I do it (I never had a class or anything, just figured this out on my own, so there may be some unusual steps in my method):
Strip the outer insulation, un-twist all the wires, straighten them out and put them in order (know the order forwards and backwards so that you can look at it from either side while working). Then pull them all out straight, bend the wires back and forth a couple of times to get the twists and kinks out, you want them to be perfectly straight before you attempt to put on the connector. If they don't straighten out easily, use a needlenose pliers on each individual wire if necessary. That's the time-consuming part. Then, put the straightened wires all back together in order, verify that the straight part is long enough to get to the end of the connector, and cut the ends all off evenly so that they're just barely long enough because if too long, the connector won't crimp down on the outer insulation. Then, put the ends in the connector, usually I do it with the tab facing me so that I can see better if they go all the way forward. If not, I wiggle and push some more until all 8 wires are all the way to the end of the connector. If one of the pairs absolutely refuses to go all the way, you can also pull it out, and re-straighten and pull on the wires again and then see if it'll go in. If it gets almost all the way, within two millimeters, the connection will probably still work, but if it's more than one millimeter I usually start over and re-do it. At that point, just before crimping, I triple-check the order of the wires (check it again at least twice more after the wires are in the connector but before crimping). Then crimp it two or three times to get it good and tight. If you have a more expensive crimping tool the tightness is more guaranteed to be correct the first time.

Then I don't even test it because I know I did it correctly.
 

tthh

Member
Location
Denver
Occupation
Retired Engineer
Most of the time when I have run Cat5, I just terminate it in a punch down style RJ-45 type jack. Whenever equipment is going to connect to that run then gets connected with a patch cable.
 
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