Summary: PPP and 'noisy telphone line'

From: Zhiyi Huang (
Date: Thu Jan 25 1996 - 08:49:07 CST

Sorry for this so delayed summary. I am still struggling with my PC.

But I think I've got many useful answers from you.

Thanks a lot to:
greg harrison <>
"Anatoly M. Lisovsky" <>
Alan Chan <A.Chan@CdnAir.CA>
John Petty d-4110 7-1925 <>
"Bert N. Shure" <>
hifter <>

My original question was:
Hello, Sun-manager,

Here is another question for help.

When I tried to dial into a PPP unix server from my PC using PC's PPP
or linux's PPP, I got many ramdom character, it seems to me that the
telephone line is 'noisy', which causes my login script aborted.

The modem I am using is a 14.4 FaxModem.

I replaced it with a new one, but I got no improvements.

What else can I check? The motherboard?

*** Answer from "Bert N. Shure" <>:

  Switch to isdn. Or
  you should contact your phone company. in california, it is

*** Answer from "Anatoly M. Lisovsky" <>:
   Check modem's manual and find out how to turn on V.42

*** Answer from Shifter <>:

  Adding S10=100 (or some higher number) to the end of your modem init
string may help to keep you connected amidst line noise....

*** Answer from John Petty d-4110 7-1925 <>:

  I had experianced the same problems a while back. My problem turned out to
be different terminal emulations at each end. I was told to use vt102 but
their system had mistakenly been set to tty.

*** Answer from greg harrison <>:

          Getting a bunch of garbled characters all at once upon connection
(usually when you expect the login screen) can sometimes be a sign of
baud problems. Double check to see what the max baud your unix server
will support for a ppp link. If it is less than 14.4, make sure you have your pc
and linux software appropriately so as not to exceed what the unix server can
handle. If the server can support 14.4, then make sure your software doesnt
exceed 19.2k baud. Hmm..let me try again..There are several things running
thru my mind which might be the cause (a late night last night and I am not
thinking too clearly :-) )

1) Check to see if your modem is V.42 bis capable. If so, try disabling it.
   There is a high chance that the unix server you dial into doesnt support

2) Make sure your software is set to hardware flow control and hardware
   compression only. Let the modems due the negotiating about what speed they
   should talk at.

3) See if your pcs software is set for autobaud. I.e if it cant get a 14.4
   connection, will it scale down to 9600 baud if thats all the unix server
   will accept at the time?

4) Check to see what connect rate you are connecting at when you get the
   problem. I use linux and sometimes it wants to connect at wierd baud
   rates (13200). I always get garble when this happens. I can try again
   and as long as the connection is a standard rate, it works fine (by
   standard I mean 9600, 14.4, 19.2, 21.2..etc)

5) Check to see what your unix server expects in the way of flow control?
   8 bits, No parity and 1 stop bit is typical for most dos/windows apps,
   but some unix servers want 7 bits, no parity and 1 stop bit.

6) In linux, when you get the garbage, it might be as simple as a scripting
   problem. If the account you dial into is PPP/SLip only, and you try to
   use it as dialup shell account, you will always get garbage. What manner
   are you using to dialup? (minicom? chat? dip?)

I doubt these suggestions will help your problems at all, but it might help
you stumble across something that might be causeing the problem. If you have
questions, feel free to ask and I will try to help.

*** Answer from Alan Chan <A.Chan@CdnAir.CA>:

  A few things you may want to check:

- Some cordless telephone will generate noise on the phone line. If you have
  a cordless phone, unplug it before you use the modem and see if things
  improve. This may even apply to some answering machines.

- If your phone line is equipped with call alert, make sure it is disabled
  when you use your modem.

- Make sure your PC has a newer serial port chip, commonly referred to as
UART (Universal Asynchronous receiver/trammitter). It should be a 16550
  or compatible. Older PC has a slower chip which has problem keeping up
  with a fast modem. You can find out what you have in your system by
  running \dos\msd.exe.

- Random characters at login may also means the baud rate is mismatched
  between the remote system and your PC. Some modems do not do autobaud
  (automatically adjust modem speed to remote modem) very well. This could
  be a problem with your modem or a problem with the remote modem. You may
  want to disable autobaud at your modem and set it at a fixed speed same
  as the remote modem.

        Judy Z. Huang Tel:(908)699-3551 Beeper:(908)633-3181
Bellcore, 6 Corporate Place, Piscatway, NJ 08854-4199

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