external usb modem

[Stefan]

Hello all :)

I want to use an older telephone-system on hardy, its connected via usb:
There is no problem to load the driver.
Bus 004 Device 003: ID 057c:2800 AVM GmbH ISDN-Connector TA

 But I can not do a connection to modem, cause I dont now which device I have 
to use under /dev.
I looked to https://help.ubuntu.com/community/DialupModemHowto/Setserial but 
that wasnt helpful. The device   ls /dev/ttyUSB* is not existing and I dont 
know how to configure kppp for modem use. So something has changed under 
hardy?!
What I have to do, to get the external usb modem working?
can someone help?

tia
stefan