I have a Debian Lenny system and I've plugged in a USB 56K modem. (I know that's as outdated as a Model T, but I need it for business.) When I type "cat /proc/bus/usb/devices" I get this:
T: Bus=02 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=480 MxCh= 8
B: Alloc= 0/800 us ( 0%), #Int= 0, #Iso= 0
E: Ad=82(I) Atr=03(Int.) MxPS= 16 Ivl=16ms
From what I can find, that means the actual device file for this modem should be at /dev/bus/usb/001/002, but I know I could be wrong on that.
I'm trying to communicate with this modem. I've used Minicom, with the device I mentioned above. There are no /dev/ttyACM0 devices, as sometimes happens with a modem. I've tried all /dev/ttySx, where x is from 0 to 4, with no results. The problem with Minicom is that it can take time and a lot of frustrating keypresses to try one device after another. Also, I'm not sure the serial port speed settings are at all appropriate in Minicom for USB modems.