Telephone polarity

Old 02-07-02, 08:48 AM
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Telephone polarity

I wired telephone and data jacks all over the place in a new construction project. I followed EIA/TIA 568B standards everywhere. I used CAT 5 for everything. I followed proper conversion to attach to the red, green, yellow, and black wiring supplied by the phone co.
Now to the question:
I have bought phones and have exisiting phones from the old house and I see that the cables that came from the manufacturers are different. Some of them cross over, some don't. What effect does reverse polarity have on phone lines? Obviously they still work. Is there a disadvantage to using one reversed? Should I make sure polarity is right on all the phones.
I think red and green are my case blue/white and white/blue is swapped at the phone. All of the jacks pin out correctly. What is supposed to be the standard for the wire from the wall to the phone?
Old 02-07-02, 11:17 AM
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Telephone communications for simple systems such as those found in residences are in balanced twisted pair configurations. This means that the polarity is insignificant as long as you get the pair correct. In a standard 4-wire telephone cable running from a wall jack to a phone the inner pair is used for one telephone line connection while the outer pair is used for a second line. Just kept the pairs lined up.

Old 02-07-02, 11:21 AM
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Polarity has no effect on telephones and modems made in the last 15-20 years. Modern equipment has a series of diodes that make polarity irrelevant. I've heard of people insisting they get better reception or higher speeds when they use "correct" polarities, but that could just as well be from tightening the connections. To be "correct", the green (tip) is supposed to connect to the whiter of the pair (white/blue in your case). Red (ring) connects to the less white (blue/white in your case). These pass straight through into the phone from the wall.

-- Jim
Old 02-09-02, 12:20 AM
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Most modern phones will not be affected by a polarity reversal.

With the old rotary dial phones, with mechanical ringers, if you had one reversed, the ringer would make a tapping noise when you dialed on another. I can't remermber the last time I saw a rotary phone though...

On telephone cords, that go from the phone to the wall, the wires are supposed to cross. As in pin 1-4, 2-3, 3-2, 4-1. Not so with your cat5 network cables, which go 1-1,,,8-8.

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