Hello Friends,
I just bought a US. Robotics Message modem (External) and it works perfectly in Windows but in Linux, After the handshaking it just gives the error "NO CARRIER". I searched the forum but could not find any answer. Please help me, I am using Kernel 2.6.5

Saqib,
I had exactly the same problem manifest with a different modem (Netcomm IN5710 - TOPIC Semiconductor Corp 560 chipset - worked fine under Windows Me on same phone line, same ISP etc but not under Mandrake 9.2/10).
I experimented with different modem settings based on a different modem I have working successfully under Linux in a laptop.

I eventually got it to work by increasing the Connection Completion Timeout (modem S7 register) value from 25 to 60 seconds.

If using KPPP, the KPPP manual has a reasonable description of S-registers, AT commands, profiles etc.

To check/set and save a new setting for S7 register do the following:
1. Start KPPP and click Setup... button
2. Go to Modem tab and open modem command terminal by clicking Terminal... button
3. Issue the following AT commands (each command will respond with OK if successful):
ATZ0 (this loads the default profile)
OK (modem response)
AT&V (this queries the modem for all current settings)
(modem will respond with a set of values something like:
ACTIVE PROFILE:
B0 E1 .......&C1 &D2 .........%C3 %U1.........\K3 \N5
S03:013 S04:010...........S07:25................
.................................................................
(look for the S07:nn value and if nn is less than 60 reset it to 60 or greater but less than 256)
ATS7=60 (sets the Connection Completion Timeout to 60 seconds)
OK (modem response)
AT&W0 (saves the new setting to profile 0)
4. Close the KPPP Setup dialogue and try to connect

I hope that this helps.

Thankyou my friend!
I already succeded in running the modem in Linux by setting the appropriate baud rate i.e at 57600. I dont know why, but it seems that the modem works right at baud rates greater than this in windows but in linux, I have to set it at 57600. Anyways, thanx again for helping.

I had exactly the same symptoms and found that the S10 register can workaround this problem. Basically it will put the units (in tenths of a second) that you can the modem can tolerate lack of detection of a carrier before it disconnects and puts out the infamous "NO CONNECTION" message. You can tell it to tolerate very long intervals of loss of a carrier but setting it via ATS10=255. For most people AT=S10=60 means a loss of carrier for 6 seconds (due to noisy phone lines, defective modems, etc) will be tolerated. The normal default is 1.4 seconds(S10=14).



cheers,
PeAK