To run a Gigaset USB Stick 54 under Linux you need to execute the following steps:
The Chipset is zd1211rw. You need to get the appropriate firmware. Furthermore you need the wireless tools to manage the stick
aptitude install wireless-tools zd1211-firmware
If you cannot find the zd1211-firmware you need to use other sources. For Debian you would need to include non-free.
Now connect the device to your system. It should automatically load the kernel module. To verify check if you can see wlan0 when executing the following command:
Now you just need to start the interface:
ifconfig wlan0 up
To connect to a Wireless network you still need to configure it. The easiest way to do it is with the NetworkManager under Gnome.