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split pairs

split pairs

split pairs


i have been stumped. someone asked me a question i really didnt know the answer to. they had wired their SNI to a 66 block, using a run of Cat5e. they used the orange wire and the green wire. I know that you are supposed to be using wh/bl for line 1. they said that they didnt get dialtone, is this because of the split-pair "made up" color code they used?

jeff moss

RE: split pairs

Well...It is typical to use the white\blue pair in some cases.However,you can make a single one pair connection using any pair as long as that pair is terminated the same at each end. EX: White\Blue - White\Blue.

RE: split pairs

what i meant is:
i know that white/blue pair is used most of the time. but the person who asked me used one wire from one pair and another wire from another pair. so that would be split pairs, right?

jeff moss

RE: split pairs

Yes, that would be splitting a pair.  However, it should not prevent you from getting dial tone.  As long as you have two wires from the active line in the SNI to the phone, they should be able to deliver 48 volts there.  When you pick up the phone, you drop a 600 ohm (or so) resistance across the line, which the CO senses as off hook and sends you dial tone.  People who don't know how to wire routinely just pick two colors and do that.  However, you will likely have a hum on the line since there is an imbalance between the two wires.

It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD

RE: split pairs

They will need to be using the orange and green wire at the jack also, to get dial tone. For only one line, the split pair does not matter. It's not RIGHT, but it doesn't matter. For years, the standard inside wire was "quad", 4 conductor (green, red, black, yellow) which had NO twist in the pairs. Most happy homeowners look at the green/white conductor and think that's close enough to green, and the orange/white and figure that's supposed to be red, and go ahead and hook it up that way. Now, when they add a second line, they're going to have crosstalk something terrible.

If they ran to a 66 block first, the jack is probably set up 568A/B, so the dial tone is getting to the block, but not to the jack. The best approach is go backto the SNI and hook up the white/blue, blue/white to the line, check the cross-connects or bridge clips at the 66 block, and double check the jack wiring.

RE: split pairs

i told the guy exactly that, rewire using that wh/bl pair.
thanks for the advice

jeff moss

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