Modem keeps disconnecting

Posted on 1998-05-04
Last Modified: 2011-09-20
I have been trying to get my plug n play card to work correctly with linux for a while now.  I can can actually dial my ISP or some BBS board successfully.  The problem is that I cannot stay connected for no longer than a couple of minutes before I am disconnected, and returned an error 'No Carrier'.  If I am quick enough to get a file to download, I will stay connected until the file is completely downloaded, then I'm disconnected.  I assumed then that the CPU provides the plug n play card with some continuous signal to ensure online connection via Win95, which I also have
installed on my system.  I then went and bought a cheap 33.6 modem card to test this assumption.  The result, actually turned out to be the same.  That is when I am disconnected, I recieved the error 'No Carrier'.  This isn't a real easy problem to solve, and would expect a detailed answer that would explain what the problem is; how it can be solved; and if it can't be solved what are the alternatives.  Also is there a way that I could "fake" the modem into thinking that it has a signal in order to stay connected.  I am thinking to do this, I probably would need to write a device driver, something I would like to not do if possible.

As for checking noise on the telephone line, it is about as clean as it is going to get.  I also disable call waiting when I dial out, so call waiting is not the cause either.  Also, I cannot find any interrupt conflicts that may be causing this problem, so I suspect that this isn't the problem either.

I need all the help that I can get on this matter to solve this problem.
Question by:shipley
  • 2
  • 2

Author Comment

ID: 1584257
Edited text of question

Accepted Solution

natmak earned 100 total points
ID: 1584258
use a kernel compiler with the serial driver intergrated (not in a module)


Expert Comment

ID: 1584259
Some questions:

a) What chipset is your modem?
b) What chipset does your ISP use for their modems?

Call your telco and ask them to do a silence test. If you're in the UK get a NETCOM account and do their modem-info test to give you a graph of attenuation.

Try writing S10=254 to the modem as part of the init.

If it's a PnPray problem, you could try running isapnptools (search Altavista for that). But if a "cheap modem" gives the same result then you're looking at a line problem. Move all your modem cables away from power sources. Disconnect any other telephony devices on the line.  

Run irqtune to increase the IRQ priority (this made a lot of differnce for me a while ago with RH 3.3.3).

Finally, after all that, get an engineer from the telco to check your line.

Author Comment

ID: 1584260
I tried adding S10=254 to init string, but the modem reported an error.  As for irqtune, I cannot locate it on my linux system.  My modem is a 336F by Best Data (Smart One Series).  What else can I try to get my modem working properly.

Expert Comment

ID: 1584261
You could try forcing a V.FC connect - +MS=74 off the top of my head - check out the manual. If this holds the line, then you're looking at line noise in the high range which upsets V34.

Featured Post

How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

Join & Write a Comment

I have seen several blogs and forum entries elsewhere state that because NTFS volumes do not support linux ownership or permissions, they cannot be used for anonymous ftp upload through the vsftpd program.   IT can be done and here's how to get i…
Note: for this to work properly you need to use a Cross-Over network cable. 1. Connect both servers S1 and S2 on the second network slots respectively. Note that you can use the 1st slots but usually these would be occupied by the Service Provide…
Sending a Secure fax is easy with eFax Corporate ( First, Just open a new email message.  In the To field, type your recipient's fax number You can even send a secure international fax — just include t…
This video shows how to remove a single email address from the Outlook 2010 Auto Suggestion memory. NOTE: For Outlook 2016 and 2013 perform the exact same steps. Open a new email: Click the New email button in Outlook. Start typing the address: …

705 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

18 Experts available now in Live!

Get 1:1 Help Now