Second Phone Line won't hang up 3

[wjl11]

Hello,
My house is wired for 2 lines throughout. We use a splitter in each room so that line 2 can be used for modem activity.
Suddenly, in one of the rooms, after the modem is used, the line does not disconnect. The computer thinks its disconnected, but the line stays open. When you pick up the phone to listen it is either dead or the has the noise that indicates the phone is off-hook.
I checked the wires in the wall and all is connected and looks OK.
BTW, these connections are daisy-chained from room-to-toom.
Any ideas on what is wrong?
Thanks,
Will

 

[executone]

Your modem could be bad on that computer and holding the line offhook. When this problem occures unplug line from that modem. If line returns to normal operation, the problem is that modem.

Good Luck!!

 

[JeepCrazyKid]

i had this problem. the relay that initiates the hangup in the modem is bad. (the click you hear before the modem draws a dialtone and right before you hang up). you can test your theory by plugging in a regular phone to that line and testing or testing your modem on another line.

 

[wjl11]

Looks like it was the modem.
Thanks!

 

[tbirnbaum]

I've recently been experiencing a problem similar to what is described in this old thread.

I was on a call, getting what sounded like AM radio interference. The other party did not hear this. I had been on the line earlier both for a few telephone calls and using my modem, with no trouble. We decided we'd hang up and I call him right back.

I found I could not, however, disengage the phone line. Depressing the switchhook did not yield a dial tone, and eventually I received the off-hook indications.

I reset the phone line by unplugging everything from all the jacks and replugging it all in. Then I had a dial tone, and was able to make a call. Ah, but once I tried to hang up that call, I could not, and the AM radio was back.

After much troubleshooting of all the wires and equipment, I isolated the problem to the modem. When the modem alone was plugged into the jack using a good wire, even when disconnected from the computer and the electrical line, and I would check using a good phone and good wire on another jack, the system would be screwed up in this way. With the modem out of the equation, the good phone and good wire worked fine on both the jack in question and the other jack.

So, I figured I had successfully isolated the problem to the modem, some sort of short or something.

Then, as a last test, I plugged the modem and good wire into the other jack, and found that this did not screw up the system! How could it be the modem, if the modem did not screw up the system on the other jack? But how could it be the jack, if everything else worked fine on that jack?

It's some sort of combination of the modem and that particular jack, it seems.

Note that the modem doesn't have to be in use. As opposed to the earlier poster's experience, the problem does not occur only after the modem has been used. This problem arises as long as the modem is plugged into that particular jack, after any equipment makes a call and attempts to disengage the call.

It seems so strange that simply having a piece of equipment plugged into a jack, not in use, not pulling any electricity, and with nothing daisy-chained off of it, could cause a problem, and it seem even stranger that it only happens on one particular jack, a jack that works fine in every other way.

Right now what I'm having to do is keep the modem out of the equation, and then when I need to use the modem, I hook it up, and then when done I have to unhook it, and then I check using the phone that I have a dial tone. Very troublesome. I know a more permanent fix would be to hook the modem up to another one of the jacks, but this would be more inconvenient due to location.

I hope I've explained this clearly. Can anyone offer insight as to what is causing this trouble and how to fix it?

Thank you!

 

[tbirnbaum]

P.S. I only have one telephone line, not two lines like the earlier poster.

 

[ISDNman]

One possibility is that the modem has a defect that only affects the Yellow/Black pair typically used for line 2. Possibly the jack that shows this problem has the yellow or black touching the main red green pair.

Thats pretty much the only scenario where I could see the jack making a difference.


Hmmm, actually here is one other possibility - I suppose the "fault" in the modem could be polarity sensitive. Not too far fetched in that there is sometimes a brisge rectifier. If one diode were shorted you 'd have this symptom with one polarity but not with the other polarity.

 

[bkrike]

ISDNman has a good thought in the polarity issue, and the second pair theory. One of the jacks may have its polarity reversed from the other. You would never know the difference, but a bad piece of equipment (modem) might.

Another reason for the different jacks scenario could be this: The problem you describe sounds like a short in the modem that keeps the dial tone open. When shorts are new like this, and don’t completely kill the dialtone, just moving the defective equipment around (banging it, etc.) can cause the short to increase, decrease, or leave. I think you just need to replace the modem.

 

[tbirnbaum]

Thank you so very much for your responses, folks. I do appreciate it. This is a nice forum!

I had checked the jack when this trouble began, and, though the ouside was fairly dusty and I wondered if that caused some trouble so I tried to clean it out, everything inside looked new and shiny and unbroken, and I didn't know for what else to look. I will check the wires in the jack again, paying particular attention to seeing if the pairs are touching, though I don't know how they might have shifted, causing this problem to begin earlier this week, as nothing has been banging against the jack, which is in an inaccessible area.

For the polarity issue, is this something that could crop up suddenly? This modem and my line have been working fine for a long time, and it sounds like polarity reversal is something binary, not some problem that eventually happens. I'm afraid I don't have enough knowledge to really follow what is being described about faults and rectifiers and diodes. I'd be grateful if you could explain this to me and advise me as to what I could check.

I believe that it could be a short in the modem, and I understand from what you point out that what could seem like the jack making a difference was actually the banging around of the equipment making a difference. At first when I found that the trouble didn't arise at the other jack, I thought maybe it was as you explained, that banging it around -- actually I thought perhaps it was the dust in some way -- had cleared up the problem. So, I brought it back to the original jack, and the problem was there. I've checked back and forth at both jacks several times, and the results stay the same, so I don't think the short is increasing and decreasing and misleading me.

So, it still seems like a combination of problems. What I'm understanding now -- is this what you mean? -- is that perhaps a short came about in the modem (something new), and the jack has the polarity reversed (something static), and this in combination causes the trouble to manifest only with the modem at that jack, but where the polarity is fine at the other jack, the trouble doesn't manifest. Does that sound right? What causes a short? (There hasn't been any lightening.)

Is what I do to reverse polarity simply switch the locations of the pairs, by unscrewing the little metal parts holding the ends of the wires in place inside the jack, unattaching them and then reattaching them to the opposite little metal part? Before I bother switching it, is there a way to visually see if polarity is correct? I think my friend tested with a voltmeter many years ago, but that may have just been for general activity, not polarity.

Even if that works, will the short increase and I'll need a new modem anyway? I sthere a way for me to fix it?

What kind of a chance is there that something is wrong with the line wiring in the basement?

Thank you so much!

 

[bkrike]

Your detailed post is correct. Polarity is static, and you can reverse it by swapping the pairs. To tell you the truth, I would have never even thought that a polarity sensitive problem could arise with a modem; until I just read it from ISDNman. But it does sound plausible, so you can test it. Perhaps re-terminating the jack will clear it up.

As a phone and cabling guy I have never really researched why shorts in equipment happen. I just know from experience that sometimes stuff goes bad

I am assuming that the other phone jack you are testing with is live, and has the same phone number as the one with the problem. Your described problem is strange.

You can test the modem itself by putting a meter on it. You take a phone cord, plug one end into the modem and strip back the other ends two center conductors so that you can put probes to them….I always used an analog KS meter, and have never gotten around to judging shorts with a digital readout.

Let us know what you find.

 

[tbirnbaum]

Thanks again!

Re-terminating? Ah, that must mean dis- and re-connecting the wires to the terminals in the jacks -- what I was unprofessionally referring to as the little metal parts -- but not necessarily switching the polarity, is that right?

Yes, this all involves one telephone number, one line. All the jacks involved in testing are live and, when the modem is not part of the equation, work perfectly fine with telephones.

That's really useful information on how to use a meter to test the modem. I don't myself have the voltmeter; it is my friend who has one, an analog one. If we were to do the testing as you describe, for what would we be looking in the readout? The modem works, is not completely broken; I am using the modem right now, but once I am done, I will need to unplug it from the jack to reset the line, as otherwise the line won't hang up. So, for what would we be testing with the meter, how would the readout tell us about a short?

Since this modem is somewhat broken now, will it now progressively get worse? Does the answer to that question have to do with the part about faults and rectifiers and diodes, which I do not yet understand?

As a further test, I just plugged a different (older, slower) modem into the jack. That other modem didn't cause any trouble, and, as we already know, nor has any of the other equipment. So yes, there really must be something wrong with this modem.

A remaining question is what is wrong as well with that specific jack, so that in combination the trouble manifests. I will, after I get offline, I guess I should try switching the polarity. May I ask again, is there no way to visually match the polarity correctly? I guess I'll at least play around with the re-terminating, as you put it.

The telco repair thinks there is something wrong with the line coming in from outside up through the jack, and that I will need to have someone come out to check into what the telco is calling a transmission problem with one of the jacks.

Thank you very much for your help. I will of course let you know what I find. You are great for bearing with the gaps in my knowledge. (I hope your mention of my previous post as detailed is a good thing.) I also appreciate your validation of the problem I am experiencing being strange!

Thanks!

 

[tbirnbaum]

Wow! The switching of the polarity seems to have done it! Yay!

I read up on diodes and bridge rectifiers at Wikipedia (

http://en.wikipedia.org/wiki/Diode_bridge)

and other places online, and now I think I get it. The bridge rectifiers allow items to work with either polarity, so in my case, it indeed made the short polarity-sensitive. With the polarity reversed, the shorting diode is no longer part of the path used, and thereby the modem causes no trouble. This is indeed the reason there was a difference between the two jacks; the other jack must have already had the opposite polarity.

That everything is now functional doesn't change the fact that the modem is still a little broken, still has the short. The modem has a problem, but we luckily have a workaround. The reason the trouble manifested suddenly on Monday was the modem shorting, something new, and the workaround involved reversing the polarity of the jack, something static. If one of the diodes in the current path being used, the path being used with the current polarity, shorts out, then the modem will cause trouble with a jack at either polarity. (I wonder whether the modem is on its last legs.)

So the problem was in the modem, but we took advantage of the bridge rectifier, and now with the switched polarity that defective diode is bypassed, no longer involved.

What's still weird, however, is the type of trouble the modem's been causing. It isn't that it hasn't been working at all, or that it causes the trouble I've been experiencing only after using it or some equipment daisy-chained through it. It puzzles me that the modem alone, hooked up to the jack pre-polarity reversal, not being used, not turned on, not attached to anything else, only the modem attached to the jack with a good wire, could cause trouble on the line even when the phone I was using was on another jack, when the situation didn't involve a call going through the modem at all. Somehow the defective equipment disturbed the line just by being plugged into the jack, even when it didn't seem to be involved all in the use, not part of what I would think of as part the circuit and in a position to disrupt.

In any event, I am pleased. I am very thankful that I found this forum and to the two posters who patiently and kindly helped me.

Thank you so much!

 

[jerryreeve]

When a phone line is idle there is a 48VDC battery on the line, your modem is ignoring this condition until the 90V ring or the loop closure cause a changing condition within the modem that basically causes the relay/solid state relay to close. that same defect is what is holding the relay closed until you manually disconnect the wires that cause the telco to put the 48VDC back on line again and you start over.

I have seen this about 4 or 5 times in the last year, modem or phone works fine to make a call out but then the modem will not release the call even if it was not part of the actual call itself.

Always check the modem first.

If you have a two line setup in your house with a modem on it, get a single pair wall cord (only has two pins on the plugs) and keep the second line (Black/Yellow) away from the modem.

----------------------------
JerryReeve
Communications Systems Int'l
com-sys.com

Mind like a Steel trap - Once used forever clamped shut.

 

[ISDNman]

Glad you are up and running.

To answer a few questions:

The diode may have been weakened by a surge longe ago and took some time to go dead. Or it simply could have been a manufacturing defect (in the diode) that took a while to fail.

Or possibly the diode may have died a long time ago but the polarity of the line changed. Yes, normally line polarity is static, but if the Telco cut over a new cable there is a fairly good chance these days the polarity will be swapped (in the old days the Telcos were very careful about polarity, but this is no longer the case). Modern equipment is not polarity sensitive but some of the older Touch Tone phones are polarity sensitive. Presumably the two jacks have had opposite polarity for quite some time.

As far as your modem is concerned, if our theory about the bridge rectifier is correct then there is no particular reason to expect it to die completely soon (though if the diode was damaged by a surge the othe rdiodes may have beeen stressed at that time).

Happy new year