lspci -v listing results of the modem
00:0b.0 Serial controller US Robotics/3Com 56K Fax/Modem Model 5610 (rev 01)
(prog-if 02 [16550])
    Subsystem: US Robotics/3Com = Unknown device 00d3
    Flags: medium devel, IRQ 9
    I/O ports at ec00 [size=8]
    Capabilities: <available only to root>