So first, you need to get the hardware to work correctly under Debian. Plug in your E160G and check dmesg to see if the device recognises correctly. If you see ttyUSB0/ttyUSB1 appear you can skip this step.

First, you need to download USB_Modeswitch:

# wget http://www.draisberghof.de/usb_modeswitch/usb_modeswitch-0.9.4.tar.bz2
# tar jxvf usb_modeswitch-0.9.4.tar.bz2
# cd usb_modeswitch-0.9.4/
# ./compile.sh

Now you have the usb_modeswitch program, as this will be executed by udev it needs to be in a sensible location, personally i’d copy it to /usr/local/sbin/

# cp usb_modeswitch /usr/local/sbin/

Also, you need to grab the latest config file from the usb_modeswitch website and put it into /etc

# wget http://www.draisberghof.de/usb_modeswitch/usb_modeswitch.conf
# sudo mv usb_modeswitch.conf /etc/

Now, by default the config file comes with the section commented out, so edit the file and uncomment the section for the E220 (which is essentially the same device).

# sudo $EDITOR /etc/usb_modeswitch.conf

One last step, you need to add a small configuration file to udev to detect the E160G and run usb_modeswitch, put this file in you /etc/udev/rules.d/ folder:

SUBSYSTEM=="usb", SYSFS{idProduct}=="1003", SYSFS{idVendor}=="12d1",
  RUN+="/usr/local/sbin/usb_modeswitch"

Restart udev, and plug in your E160G…

sudo /etc/init.d/udev restart

and you should see something similar to:

[   16.085904] usb 5-3: GSM modem (1-port) converter now attached to ttyUSB0
[   16.086033] usb 5-3: GSM modem (1-port) converter now attached to ttyUSB1

So, the device is detected and you have your USB ports, first a quick overview. The E160G shows two serial ports, one is a data port, the other is for control signals. NetworkManager only makes use of one of these ports but the Vodafone Connection Manager uses both. Now you have a choice, install Network Manager 0.7 to gain native GPRS/UMTS data support or use another package. I went for Network Manager, while it’s still in beta and i’ve had a few run-ins in the past with it I decided to give it a go.

So, it was a simple case of adding the 0.7 repositories to /etc/apt/sources.list, updating, then installing the needed packages.

# echo "deb http://debs.michaelbiebl.de/ unstable main" >> /etc/apt/sources.list
# apt-get update
# apt-get -t unstable install network-manager

You might need to remove any old Network Manager packages before you do this, as network-manager-openvpn collides with the new package.

Hopefully thats give you the overview you needed, and you should be up and running!