How to test phone line polarity w/ multimeter?

This WAS the message "Phone makes terrible sound w/ ans machine"
I am now checking the phone line, but dont have one of those little LED testers. The green and red wires are connected to the correct screws on both ends, but there could be a splice in the crawl space under the house, and I am not crawling under there in this cold weather.
I have a digital, and an analog Multimeter. How can I test to be sure the polarity is correct using either of these meters?
Thanks
Mark
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Hi, Just swap the leads and see if it corrects the problem. White striped wire is tip and solid color is ring. Like white/blue - blue in a pair. Tony
snipped-for-privacy@UNLISTED.com wrote:

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Thanks
Except I only got solid wires. One red, one green. I did find that with the meter set to DC, if the red wire from the meter is put on the red phone wire, I get a negative voltage reading of about 52 volts. Reverse the meter leads and I get a positive reading. This is the same on all phone jacks, and on the main phone company box outside. That tells me that all phone jacks are the same polarity, but I wonder if the phone company wires are not reversed. Both are black, so how do I know? This is possible too, because I had a porch built, and that phone jack was moved. The wires were disconnected because they were too long after the move. So, I do not doubt they could be reversed. After all, both are the same color.
Is there a standard where the red should be POS. or NEG ??? Which is which, and how does that compare with ring and tip (I never understood that)?
Thank U
Mark

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Green= tip, Red= ring. Yellow= tip, Black= ring.
Remember the tip is the positive (ground) terminal and the ring is negative. Historically phones were all negative with respect to ground.
Black (neg) meter lead to the tip and red (pos) meter lead to the tip should indicate a negative voltage.
RB
snipped-for-privacy@UNLISTED.com wrote:

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You mean the Black (neg) meter lead to the tip and red (pos) meter lead to the RING, right? (you said TIP for both).
If that's the case, that is what I have.
Red meter lead on red wire = negative voltage.
By the way, I have now checked polarity on every wire, and from what you just said, it appears the polarity is correct. I eliminated the modem entirely, changed all the phone wires, and swapped answering machines. After all of this, I still had the problem. However, when changing phones, the problem is gone.
The guilty phone is almost brand new. I bought it a few months ago. It's a Lenoxx PH-319. The phone itself is great, sounds good, looks good, even has a headset, and it was cheap to boot. But the cheap may be the problem. When I plug in an ancient "princess phone", the problem is gone. I just emailed the Lenoxx company. Lets see what they say.
Thanks
Mark
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Sorry about my error. Your interpretation is correct.
I looked at the on-line manual for this phone and may have found the problem on the last page where it reads "Made in China."
I found that over time we had added about a dozen phones. This past year we've had varying problems with most of them. I threw out the phones from China (8 of them) and replaced them with good quality phones and am much happier with the performance. The ones that I like best are made by Plantronics. Sony comes in a very close second. From a life-cycle cost perspective I've come to believe that Chinese products aren't worth the "savings."
RB
snipped-for-privacy@UNLISTED.com wrote:

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Most modern phones have polarity protection and can care less about reversals.
The only phones that won't work are $2 drug store phones and old Western Electric built-like-a-truck sets. Come to think of it, even some of the $2 phones have polarity protection. <G>
Barry
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The Red ("ring") should be negative with respect to the Green ("tip") wire, Also Yellow is "ring" therefore negative and Black is "tip" therefore positive if there is also a second line on the "POTS" (Plain Old Telephone Service) cable. Alternately the Yellow and Black were used for 24V (28V?) AC power from a small transformer in the house to light phones w/ lighted dials, e.g. the Princess phones. Really old cable may lack the Black wire. Ring and Tip refer to the side contact and the end contact of a phone plug, as used on old switchboards, and quite similar to 1/4" stereo headphone plugs used on Stereo receivers, tape decks etc. 48V DC nominal is present if the phone is on hook, off hook is will be more like 6-10V, and if it rings, 20Hz AC ring voltage of about 90V(?) will also be applied.
For modern Cat 3 or Cat 5 twisted pair phone wiring (same stuff used for networking) the colors become: Ring - Blue w/ White, Tip - White w/ blue for the first pair, then the same but Orange/White & White/Orange, Green/White & White/Green, Brown/White & White/Brown. POTS is obsolete and shouldn't be used for new wiring.

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Actually the phone system uses a -48V supply. Tip is neutral/ground (green) and ring (red) is at -48V DC. But it really doesn't matter if red and green or black and yellow, if used for a second phone line, are reversed, the phone will work regardless. The phone uses a transformer or bridge circuit that allows it to work either way. The DC voltage is only used through a switch to determine the off-hook condition and for pulse (rotary) dialing.
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snipped-for-privacy@UNLISTED.com wrote:

Well... it's kinda hard unless you can get the leads for your meter on both ends of the cable.
Another option might be one of the network cable testers. You connect one part at the box that sends a tone on the line, and the other part picks up the tone on the jack end.
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The "tip" lead is usually green and with the line open, it will not read a voltage, however, it will show a resistance to a earth ground, such as a water pipe, the safety 3rd pin on an AC outlet (be carefull) or the plate screw on an outlet or switch (assuming metal boxes in a grounded system). The tip side can also be white/'color' (more white than 'color') of a multipair cable where 'color' is blue, orange, green, etc. Lost yet? It can get worse. Some multipair cables have a pair color with 1 white and 2 white bands, i.e. blue/1white and blue/2white, where blue/1white is the tip. Onto the 'ring' side. It is usally red .... get it, ring ... red, r....r. It, with the line open is at -48 volts to ground, however, as most central office -48 volts is actually at about -52, it will usually read -52 or thereabouts. With the multipair cables the 'ring' side will be the blue/white (more blue than white), or orange/white, etc. Or it will be the 2white side of the pair when it is marked with the 1white and 2white markings. I hope I didn't confuse the issue too much.
snipped-for-privacy@UNLISTED.com wrote:

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> This WAS the message "Phone makes terrible sound w/ ans machine" > > I am now checking the phone line, but dont have one of those little > LED testers. The green and red wires are connected to the correct > screws on both ends, but there could be a splice in the crawl space > under the house, and I am not crawling under there in this cold > weather. > > I have a digital, and an analog Multimeter. How can I test to be sure > the polarity is correct using either of these meters? > > Thanks > > Mark > The ring is red or ridged, readable to ground, and it terminates on the right. That little limerick is to help new folks remember that it is the ring side of the line that is red and will measure ~48 volts to ground using a high impedance meter such as your digital multimeter. Run a three wire extension cord from a known grounded receptacle outlet to the vicinity of the telephone jack in question. Using the extension cords equipment grounding conductor as a reference measure the DC voltage on both conductors of each pair. The one that shows 48 volts DC relative to ground is the ring which in four conductor jk wire is the red or the yellow wire. The green or black wires should read a relatively low voltage to ground because if the standard pattern was followed they are the tip conductors of each pair but the exact value will not be consistent unless your home has an unusually good grounding electrode system with an impedance to ground of under five ohms. The names tip and ring come from the parts of a standard 1/4" phone plug such as the ones found on good quality stereo head sets. The tip is battery positive which is grounded at the exchange in telephone practice. The ring is battery negative which is forty eight volts relative to the ring and to earth ground. The polarity can also be checked with either meter by measuring between the red and green or the yellow and black and observing the polarity indicator of the digital meter or the needle deflection of the analog meter. With the meters common (black) lead on the ring conductor and its positive (red) lead on the tip conductor the meter should indicate a positive voltage. If you put each lead on the color that does not match in each pair you should get a positive voltage indication.
--
Tom Horne


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