My mobile or PDA has USB, Can I use the USB to connect to the GS-911?

Unfortunately not! Normal USB has host controllers (typically the PC/Laptop) or hubs, and the devices that plug into them are client devices... You cannot make a straight connection between two host controllers, nor can you directly connect two client devices together... The GS-911 is a USB client device, as it plugs into the PC (the host).  Your PDA/Phone is in all likelihood also a USB client device, and hence  you cannot connect the PDA directly to the GS-911, using its USB port.  Even if your device had a USB host controller, you would still need the USB drivers installed and these are only available for the Windows XP and Vista Operating system.