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Modem problem.. please help..

Murali Koppula

Joined: May 07, 2002
Posts: 10
Hi Ranchers,
I am using US Robotics 56K 5686 external modem
connected thru the serial port.
It works just fine on windows ME.
But on linux, whenever I try to use, it gives an error 17 and says "detected serial loop back".
The same modem (a different piece) used to work on the same Linux installation. I am totally confused as to what the problem is.
What should I do to make it work? Someone please help..
Frank Carver

Joined: Jan 07, 1999
Posts: 6920
Sounds like the modem has become switched to half duplex (where it echoes all input characters back to the originator).
Try starting up minicom and pointing it at the port with your modem. Then type
The modem should answer
If you see
as you are typing, the modem is in half-duplex mode.
Try typing
to reset the modem to factory defaults and try again.

Read about me at ~ Raspberry Alpha Omega ~ Frank's Punchbarrel Blog
Murali Koppula

Joined: May 07, 2002
Posts: 10
Thank you for your reply.
My modem is not in echo ON mode. I checked the way you mentioned, with minicom. It was echo OFF and still wouldn't connect.
However, I think this is how my problem started..
I bought this modem from USRobotics which is supposed to work with both V90 and V92 technology. But to enable V92, I needed to download and update the firmware from their website into the modem. Before I upgraded the firmware, it was working for both Windows ME and Linus. But, after I upgraded, it started giving this wierd error (17). message log, in addition to saying loopback detecte, it also says that it is guessing that there is no peer ppp software running on the server. I was totally clue less why it would think like that.
Now, I returned the modem and exanged it with another one (and did not mess around with firmware). It is now connecting fine and I am happily sending this message from Linux.
I am curious though, why it behaved that way after I upgraded the firmware for V92. I appriciate any of your comments on this.
(can you suggest any good modem books on the market - especially to work with UNIX(/like) OS).
Thank you.
Frank Carver

Joined: Jan 07, 1999
Posts: 6920
Ah! It's pretty obvious that your firmware "upgrade" screwed the modem. It may have put it into some sort of diagnostic mode. or just broke it.
As for books on modems, I haven't seen a modem book in many years. Modem technology is so taken-for-granted these days, people just assume it works. You may want to search the web (or your Linux CD) for things like the "linux modem howto" or "ppp howto" to get a more stp-by-step approach.
I'm glad the new one works, anyway
I agree. Here's the link:
subject: Modem problem.. please help..
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