Modems, Analog Lines and ... Electrical Lines?

About a week ago I was asking about a situation where my modem for a dial-up
account was losing the signal or getting "no dial tone" response from the
analog line. At first I assumed it may be noisy lines from too many people
on a network of analog lines. But now after today we have another theory
that seems to have merit.

For three straight days the phone line I had this computer plugged into was
working fine and getting between 37.8k and 40.0k connections to a dial-up
account. Suddenly today the connection ceased to function and would not
register a dialtone in the analog line. This happened at the exact same
time as some workers were running electrical wiring into a junction box in
the false ceilings above the area where the phone lines are run for this
computer and a few others that are capable of using these analog lines. The
credit card machines still worked fine, but this PC would not get a dialtone
out of any of the lines I took it to in that part of the building.

So can this be a possible explination? Electrical wiring ... causing some
kind of "feedback" that's loud enough to cause a modem to stop being able to
receive a dialtone? One of the people that was around when the initial
phone wiring was being done said, "The installers made sure the lines did
not rest near any electrical lines." But now we think that may have
changed, not only today but also a few days back when these same people came
in and were messing around in the ceilings adding and moving lines.

Any thoughts and/or solid knowledge on this would GREATLY be appreciated!

--
Kyle

Reply address is fake. Please send all praise, abuse, insults, bequests of
$1million US dollars to sensfan_luvslisa (at) yahoo (dot) ca. Change the
obvious to the obvious. Oh, and if you must abuse or insult, don't expect a
reply. Money gets faster attention ;o)

 

I can say that I have seen this happen. We had a setup on a dedicated line
that was used to place orders with a supplier. We had a IBM PC running
Windows, and an external US Robotics Sportster Modem connected via standard
serial cable.

There was one faulty ballast in the lights above the room. When the ballast
was acting up enough to cause the lights to flicker, we could not get the
modem to connect.

Good Luck

Fred.

 

On Wed, 4 Aug 2004 22:20:46 -0400, "Sens Fan Happy In Ohio"

|>So can this be a possible explination? Electrical wiring ... causing some
|>kind of "feedback" that's loud enough to cause a modem to stop being able to
|>receive a dialtone?


Installing a phone system, I had one line I just couldn't get to pass.
It ran right across a florescent fixture. Couldn't route it far enough
away for it to ever work without noise.

Not sure about getting a dialtone, but any modem connected to it would
have a real problem staying connected.

 

On Wed, 4 Aug 2004 22:20:46 -0400, "Sens Fan Happy In Ohio"

|>So can this be a possible explination? Electrical wiring ... causing some
|>kind of "feedback" that's loud enough to cause a modem to stop being able to
|>receive a dialtone?


Installing a phone system, I had one line I just couldn't get to pass.
It ran right across a florescent fixture. Couldn't route it far enough
away for it to ever work without noise.

Not sure about getting a dialtone, but any modem connected to it would
have a real problem staying connected.

Canceled last message to add:

There might be a work around...
edit your modem string to include S10=255
This will increase the time a modem will wait before disconnecting due
to errors.

 

First, what kind of phone wire is in that ceiling?
Information will be printed on that wire maybe every 18
inches. If no such printing, then wire is defective. If wire
is conventional four wire phone wire, then that wire must be
replaced - no more discussion. Currently, all phone wire must
be CAT-3 or better. Cat-x wire makes adjacent interference
irrelevant.

Second, open wall jack to examine connecting wire colors.
If incoming two or four wires is colored red, green, yellow,
and black; then it is defective wire. Wire no longer
acceptable for conventional (POTS) phone service.

Third, put a conventional phone on that connection. Does
the phone work normally - no noise or hum. Anything that
can interfere with a modem can also be heard by a
conventional (POTS) phone. Every other phone line must be
working; still not interfere with or create noise on a POTS
phone conversation.

Some other factors. Is the phone line connected to the
correct phone jack on modem? One says "Line". That jack
connects to wire in ceiling. A second jack says "Phone".
That is where the POTS phone is connected to verify phone
line; to listen for noise.

It remains possible that the modem has a failing internal
component. Test that modem on another phone line AND test
that credit card machine on the suspect line.

There is no solution until basic facts have been provided.
Do not try to fix this problem yet. Spent more time first
identifying a reason for problem - as demonstrated by above
procedures.

 

This is good advice and I wish to elaborate on it.

To be a bit nit-picky, the described wires are obsolete. They might
not be defective, but they are old enough that it is worth replacing
them if the other diagnostics don't give you a solution.

I have some wiring in my house that is from the late 1930s and it
still works fine. There are also several splices at various point in
the wiring and several abandoned lines. I saw no reason to replace it
since I get around 50K on dialup when I use it. If you saw it, you
would be shocked that it works at all, but it actually works
perfectly.

Again, nit-picky, but the amount of noise/interference that it takes
to cause problems for a modem is much less than would irritate a
human. You should pick up the phone, dial a single digit to clear the
dial tone, and listen. There should be no pops, crackles, hiss, people
talking, etc. on the line.

What he means is that you should have some noise on the other lines
while you are doing this test. I often take a phone in another room
off the hook, dial another extention, and place a radio next to the
phone. You will then listen to the line that you are testing. You
should not hear the radio on that line. If you do, there is something
called crosstalk and that can cause you problems.

Most modems will NOT disconnect that "Phone" jack when the modem is in
use. That is why it is a good place to plug in your regular phone to
do the above tests.

Another test is to get ready to dial your ISP, pick up the regular
phone, then commense dialing your ISP. You should hear a dial tone,
then the seven beeps as the modem dials the ISP, then ringing, then
the ISPs modem picks up the call and it starts
buzzing/hissing/squeeking/spitting etc.

It sounds like musical tones and someone clearing their throat and all
sorts of unusual sounds like that. Those last five to fifteen seconds,
going back and forth with different sounds. The technical term for
this is "handshaking". The two modems are "talking" to each other
deciding on a mutually agreeable way of communicating with each other.

Then it settles into a constant hissing sound. That is the two modems
actually doing their work. Caution, with you listening in on that
other phone, the two might not be able to complete their handshaking.
If that is the case, hang up when the ISPs modem answers.

If the modem disconnects the "Phone" jack on the modem when the modem
is in use, use a regular phone plugged into another jack with the same
line or use a splitter.

If the problem is one of speed, the quality of the line and the
crosstalk are important factors to check. If the problem is no dial
tone, it is actually a lot simpler problem. If you hear the dial tone
in the regular phone, but the modem says no dial tone, replace the
modem.

If the problem is one of speed and the tests prove that the line is
crystal clear and quiet, you may have a major problem. That is because
it may be a signal strength issue with the phone company. If it is,
you are screwed. Most phone companies will not even talk with you
about these issues.

The reason is that it is a technical problem and you will almost never
be allowed to talk to anyone who has any engineering knowledge. They
exist, but the public is not allowed to talk to them. With my EE
background, I can communicate well with them, IF I'm allowed to. It is
telephone company policy that the customer service people can solve
all problems. Okay, maybe that isn't a written policy, just an
attitude.

The last time I had a problem like this, the guy I FINALLY was allowed
to talk to said that he would change a setting for me. He said he
would be in trouble if they found out because it would place the line
outside of specs. All I know is that it give me 50K with that "wrong"
setting and 24K with the "right" setting.

It took weeks of harassing them before I could talk to him. They kept
repeating that they guarantee only 2400 baud. That is the company
policy. They couldn't understand the theory behind a 56K modem and how
it actually looks a lot like a 2400 baud modem. It was very
frustrating, but probably has NOTHING to do with this problem. I'm
just venting, sorry