Weird telephone problem

On 7/16/2010 2:54 PM David Nebenzahl spake thus:

Forgot to mention, in case it's relevant, that they also have DSL, and some of the phones have in-line DSL filters. Problem remains with or without the filters.

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That sounds to me as if the circuit has developed a "DC open", which still has some small amount of capacitive coupling through it.

The central office won't "see" that the phones have gone off-hook, and initiate a dial tone, unless the phone draws at least a few milliamps of DC current from the line. If corrosion or a wire break has interrupted one side or the other of the line, the phone wouldn't be able to draw DC current through it, and wouldn't trigger the off-hook detector at the central office.

Ringing is a different issue, as it involved higher voltages, AC (or pulsed-DC), and is handled differently by different sorts of phones. The ringing signal here in the U.S. is somewhere around 100 volts at

20 Hz, if I recall correctly. Real old-fashioned phones with real ringers have an electromagnet/solenoid ringer, coupled to the line via a large-value capacitor (agian, if I recall correctly) and they require a significant amount of ringer current to operate.

Phones with electronic ringers... and wireless phones in particular... operate differently. They really don't need to draw much current from the ringing line in order to detect a ring... all a wireless-phone base station may need to do is monitor the phone-line voltage with a high-impedance voltage sensor, and "tell" the handsets to ring when it sees a high voltage.

My guess is that: (1) you've got a broken wire or corroded connection in the path which feeds the phones that no longer work, and (2) there's enough leakage through the break to allow the wireless handset to detect the high-voltage AC which means "ringing". Hence, the wireless handset is told to ring. However, when you try to answer the call, the wireless station base tries to connect to the line and start drawing the normal amount of loop current... and it can't do so because of the near-total break in the wire.

Try using one of those red-and-green-LED "phone line voltage and polarity" detectors. I suspect you'll find that it doesn't light (either color) when plugged into one of the dead outlets, but that if you phone the house number from outside the LED will flash at least slightly due to a small amount of AC leakage past the broken connection.

Start looking for bad splices, broken wires in junction boxes, or places where rats or mice have chewed on the wiring.

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Good advice above

I want to add. you should see about 52 Volts on an idle line and 25 milliamp or greater current when off hook I think to telephone switch will work on 20 milliamp, but that is pushing it.The voltage isn't critical but the current is

Bill K7NOM

Had this happen to me too. Also had a pair of what looked like excellent wires go noisy on me every time it got damp outside! had to re-run that section of phone line inside the house walls.

The failure is probably caused by corrosion at a junction/connection. Opens up the lines in DC, no dial tone, etc. But ringing works.

The corrosion is very slight and just enough to prevent the low voltage to get to the phone and the telephone service company can't recognize that you're OFF Hook, but the 90V of ringing pops across the corrosion barrier, actually breaking it temporarily down as an arc over [that's my opinion] then when you lift the phone, nothing. If you called the number the sequence for me was: At the dead phone:

1) dead phone rings 2) answer the line, no one there! for the caller: 1) hear a ringing indication [may, or may not synchronize with actual ringing] 2) then it's as though someone answered and hung up.

The fix, redo every junction between where the lines are good right up to the phone. If you're lucky, it'll be at the junction box near the phone itself. Don't do this while phones may ring, 90V hurts! Don't sever any wires, because junctions ALWAYS fail. But if the wire is protected, it's ok to scrape a little insulation back to check for voltage on the line, stand by voltage is around -48, yeah sure. I used to scrape back insulation and connect a phone to check. It was easier than using a meter. You'll probably repair everything by simply wiggling all the connections. I found that a good mechanicl manipulation fixed everything to last about a year before the system failed again.

Check FCC Part 68, which later became IEEE ???? spec, for the operating envelope of what constitutes ON Hook and OFF Hook and all the allowed leakages and unbalances.

Back in the '84 I wrote an article for Gernsbach which was published in spin off to Popular Electronics an article entitled "Hands Free Telephone" If you can find a copy there's a bit of tutorial about Public Telephone Lines, voltages, impedances, etc. My copy's in storage and my brain...uh, what was I saying?

The easiest fix is to go to where the phone line enters the house (inside), unhook everything inside, & try a phone there. This will eliminate all the inside. If it works, try hooking up one line inside at a time to see which one's bad. Or, just get a cheap codless phone, if it's too hard to redo all the inside wires if that's the problem. If, for example, you have just sprayed for insects, you may have killed a line jack, dampness can also do this. If it still won't work the problem is outside. The phone company will generally fix the outside gear (theirs) for free. Hope this helps.

I agree with the other suggestions of poor or corroded connections, because I had a similar situation a number of years ago.

Intermittent ringing and noisy connections any time it would rain. The service guy would show up within a couple of days, when it wasn't raining, and find no problems.

This went on for months, and I had installed all new interior wiring (from the network box terminals) and new wall jacks, so I was certain the problem wasn't inside.

Finally, about 4 guys showed up, and after wandering around up 'n down the street, finally determined that there was corrosion in the jack in the network box that was making it very sensitive to moisture (probably about a $1 part for the telco), after numerous attempts of troubleshooting and finding no problems.

Punchblocks in damp locations (basements etc) can also be sources of corrosion related problems.

If you don't know the age of the wall jacks, it's best to replace them all with quality jacks, so you know that the connections are clean and secure at each jack. A little dust and moisture/humidity (or an insect) can lead to serious oxidation or corrosion problems over time.

-- Cheers, WB .............

On 7/16/2010 7:20 PM Dani spake thus:

How the hell will this help me? Didn't you read my post? I said that

*some* of the phones (meaning the wiring inside the house) work and some of them don't, so obviously the problem is inside the house.

Nope. It doesn't.

--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

Bite the bullet. Buy a box of Cat-3 (or 5) wire and start over. Every house I've ever worked on has a total cluster-f**k for the telephone wiring.

Pick a location, (a closet or such) and call that "home". Run a new cable from the telephone company POE, to there. From there, run a new cable to each and every jack in the house.

One Type-66 split block and a package of jumper clips will make a nice "distribution" point in the closet.

Problem solved.

And if you decide to get campy and put in a cheap PBX, all your work is already done for the most part.

Jeff

--
?Egotism is the anesthetic that dulls the pain of stupidity.?
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com

That would truely be a miracle, and if it happens they should also consdier buying a handful of lottery tickets. Heck, just one lottery ticket, it will win.

You didn't mention this: What happens if you move a non-working phone to where a working phone is? Does it now work? If so, then it's a wiring issue. Otherwise, it's the phone itself.

Also, if you have the newer interface where the phone company connects to the house that has RJ jacks in it, take all of the phones to it and test them with that jack.

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On 7/18/2010 5:46 AM Andrew Rossmann spake thus:

Well, I didn't test that, but I did the reverse test which shows that the problem is the wiring, not the phone: I took a working phone (a regular, non-cordless phone) and plugged it in to a non-working phone jack. It was dead, so the problem appears to me to be the wiring.

The phone that rang on an incoming call, by the way, was a cordless (i.e., powered) phone, which tends to confirm the diagnosis someone else here gave of a "DC open", a corroded connection that would pass enough of the higher ring voltage to make the phone ring, but not enough to go "off hook".

--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

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There is probably a break in L1 or L2 at a daisy chained jack. Down stream of the break, there is no DC path for loop current to trigger dial tone, BUT, since the ringer is AC, there can be a path back through the ringer of a phone bridging the break [effectively two phones in series] so the phone could ring, but not close the DC loop when taken off hook.

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EXCELLENT!

That would account for the electronic phone ringing very well,

Bet the old ATT 'dialer' phone has a weak ring, right?

Agree re: corroded wiring connection as likely cause.

Go to each jack and put a *milliammeter* across Tip-Ring. Start at the demark.

You should see 20+ mA. If you don't, it's the wiring or jack.

As a next step, put the meter in series with a phone, and see if the off-hook current is still >20mA.

The first indicts the upstream wiring; the 2nd is likely the phone.

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The milliampmeter should be in series with a 400 Ohm resister. The resister represents the resistance in the phone.

Bill K7NOM

Not needed at all, and misses the point. The phone is not a fixed resistance; it's a small voltage drop that varies with loop length.

The outside plant loop and the line relay at the CO limit the current. Let's say you are 5000 ft from the CO; that's 250 ohms right there. The line relay is say 500 ohms. Worst case, 60 odd mA. In reality the line card will limit it to far less.

Nothing you can do to your end of the loop will damage anything.

Your goal is to see the max available current. If it's not sufficient at a jack, but is at the demark; there must be a bad splice in the IW. And measuring the voltage with a open circuit is sorta pointless.

--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433