Replace RJ11 line with RJ45

[MyLeftNut]

I was thinking of replacing my existing rj11 line which runs from my wall jack to the small grey box at the end of my place. This line was installed only 2 years ago for my dry loop dsl, but I'd like to replace it with rj45. I read that all current installations no longer use the old 4 wire cabling anymore and that cat5 cables are used instead. The phone line currently installed has been abused, stapled to the wall, and moved around and I know it does not maintain the same integrity it once had. So I'm hoping that I can install cat5 cabling for a better signal in preparation for an ADSL2+ installation.

Will cat5 cabling offer cleaner signals at be more resistant to interference compared to the old 4 wire telephone cables? Also, with the wiring on the cat5 cable, does it matter which pair I use to replace the old telephone wires? As long as the other end of the cat5 pair which gets screwed into the telephone jack on the wall corresponds to it's line (of the chosen pair) right?

 

[xylem]

Cat5 (100-mbps rated) should be more resistant to noise than cat3 (10-mbps rated) that, i think, was used for telephone line installations for a long time. Any of the wire pairs in cat5 should easily support ADSL2+, but each color has a different respective number of twists over a given distance; If you cut open a small piece of cable, you will probably be able to tell the difference.

 

[skyking]

Will cat5 cabling offer cleaner signals at be more resistant to interference compared to the old 4 wire telephone cables?

No. Consider that before that cable gets to your house, there are thousands of feet of, you guessed it, cat3 wiring. It supports DSL applications just fine.

 

[MyLeftNut]

So which colored pair should I chose to use in a Cat5 cable? Which is the most densely twisted pair of the 4? One site explained that the blue pair and orange pair are the replacements for the Cat3 telephone wire's red+green and yellow+black. I assume those were chosen due to the twisting density, hence higher resistance to interference. Anyone have a link that would show the twist specifications of the different pairs?

 

[mpilchfamily]

The wires are all the same inside the cable. so it doesn't matter what color pairs you use as long as you keep it strait as to which pair is on which side of the connectors.

 

[MyLeftNut]

Well there is a technical difference in twists between different colored pairs, although it might not make a difference in a telephone cabling usage. Regardless, I'd like to know the specifications for the twists of each different colored pair.

 

[kevnich2]

I always use the blue/white pair for pair 1 for phones (if it's one line).

 

[ScottMac]

Originally posted by: mpilchfamily
The wires are all the same inside the cable. so it doesn't matter what color pairs you use as long as you keep it strait as to which pair is on which side of the connectors.

That's totally wrong. Completely and totally wrong.

There are two acceptable standards for structured cabling (TIA/EIA 568a and 568b). Failure to use the standards will cause unpredictable performance and unstable communication; in most cases, severely sub-optimal performance.

 

[ScottMac]

Originally posted by: kevnich2
I always use the blue/white pair for pair 1 for phones (if it's one line).

The blue/blue-white pair *is* pair one, and belongs on pins 4&5.
The green or orange pair straddle that, going to pins 3&6
The orange pair is pair three and goes to pins 1&2
The brown pair is pair 4 and goes to pins 7&8

The difference between TIA/EIA 568a and 568b are the positions of the orange and green pair. 568a has the green pair on pins 1&2, 568b has the orange pair on pins 1&2.

There are a bunch of other rules for running an terminating UTP. Google on EIA/TIA 568 to get the list. They relate to proper strain relief, bend radius, pulling tension, crush/deformity of the sheath, etc.).

 

[MyLeftNut]

So I've been looking up this topic and this is what I found. With Cat6 the twists alternate in density along the length of the pair relative to the the other pairs as to achieve a different twist to length ratio. While on Cat5, the each pair has specificly differnt lengths due to higher or lower twist ratio. But for Cat6 specifications and the way it works, the length of the pairs can not differ like in Cat5 as it will cause propagation delay of each pair. Correct me if there's anything here that's wrong.

Seeing that the blue pair is the one most used in Cat5 signals, that it's usually the 1 of 2 pairs used in 100mbit transmissions, I would assume that would be the pair with the highest twist to length ratio?

 

[ScottMac]

You are not understanding correctly.

Ethernet and Fast Ethernet use pair 2 & 3 (pins 1&2, 3&6). GigE uses all four pair to send and receive in both directions concurrently.

The difference in length of the pairs due to varying twist count (but usually more by the difference in insulator material used to coat each individual wire) can cause a variation in delay of a signal that is transmitted concurrently down multiple pair (it's called "Skew" and there is a specification for it).

For all varieties of Category rated cabling, the pair twists, as well as the position of the individual twisted pair relative to the other pair (the "lay" of the cable) has always been variable by cable and manufacturer ... as long as the cable met the electrical characteristics defined by the Category spec. There is a mandatory minimum twist defined in the spec, but it is so small it is virtually non-existent.

The blue pair is typically "Line 1" for voice, Pair two corresponds to "Line 2" and so on. For Ethernet or Fast Ethernet (pins 1&2, 3&6 ... or pair 3 & 2 respectively), and voice (on pins 4&5, Pair 1) could co-exist ... but it's not spec and it's specifically *NOT* recommended. It jacks up the crosstalk spec (reducing the performance of the Ethernet), and the ring voltage on the phone line (90-120 VAC @ 20Hz) can cause damage to the Ethernet Transceiver.

Google on TIA/EIA 568 and read up on it.

The other major point that is frequently missed is that Category rated cabling is called "Structured Cabling" because it can be used to transmit virtually any electrical signal with the proper balun or matching device. It can be used for video (baseband or broadband), audio, serial, a variety of networking, 3270, 5250 terminals ... nearly anything ...

 

[MyLeftNut]

Thanks for the detailed response, however, my intent was not the find the difference between the two cable types and I am very aware of the difference in number of pairs used between 100mbit and gbit. I am just stating that there are infact pairs with varying twists and also that there is a difference in the twist method between cables rated for 100mbit and gbit/10gbit.

 

[ScottMac]

Well, yes. But there is also radical differences between Cat5 cables from different manufacturers, or even different cabling lines from the same producer (same for Cat5e, or Cat6, or Cat6a).

For any given specification, there are a number of ways to achieve it. There is no specific mechanical spec ("You ,must have X number of twists per foot/meter") only a group of electrical specifications relating to DC resistance, overall impedance and permitted variance, permitted levels of the various types crosstalk, individually and the power sum, measured skew ... stuff like that.

So to say "the difference between Cat 5 and Cat 6 is the number of twists per pair" while superficially true is not really accurate. The things that make Cat6 "better" than Cat5 (what contributes to the improved performance) is more than the twist count, or twist ratio, or the lay, or the dielectric characteristic of the wire coating or sheath ... it's all those things and more, as engineered by the producer of the cable.

In the case of Cat5 vs Cat6, most, if not all, Cat6 UTP will have an "X" member acting as a barrier and stabilizer/positioner for the individual pairs ... that is rare or non-existent in Cat5 UTP.

Your statement would have been just as accurate and relevant if you'd said "Some Cat 5 comes in beige color sheath, and some Cat 6 comes in blue color sheath; both types come in colors that start with 'B'." Accurate but meaningless.