The new usb modem from Reliance EC121 is different in the sense that it has usb storage has the MS Windows drivers onboard; when plugged in for the first time it acts like a flash storage and start installing the driver from there. After that (and on every consecutive plugging) this driver switches the mode internally, the storage device vanishes (in most cases), and a new device (like an USB modem) shows up.

Well this thing in window used to confuse the earlier linux kernels. But guess its not the case anymore. There is something called usb_switchmode for selecting the usb device. But it was rather useless. I was able to connect my ec121 using the instructions herein..

http://www.hasanen.com/?p=25

Edit your /etc/wvdial.conf

Init1 = ATZ

Init2 = ATQ0 M1 L1 X3 V1 E1 S0=0 &C1 &D2 +FCLASS=0

Modem Type = Analog Modem

ISDN = 0

Abort On No Dialtone = False

New PPPD = yes

Phone = #777

Modem = /dev/ttyUSB0

Username = 10digitReliancePhoneNumber

Password = 10digitReliancePhoneNumber

After this, you should use wvdial as root
This will give some output and will show the primary and secondary dns entries. Unfortunately, For some reason wvdial doesn’t change the DNS name servers so you have to do it manually :

Edit /etc/resolv.conf in your favourite text editor and add the following :

nameserver {the ip of your priimary dns}202.138.103.100 for me

nameserver {the ip of your secondary dns}202.138.96.2

Close the connection and reconnect. It should all work fine for you now