This is a dreaded software modem and as such is not recognised by Linux.
You will need to buy a PCMCIA modem card which uses the Lucent chipset.
I use a Tashika V.90 card and it works well, with one caveat: because the Ethernet interface is integrated within the Toshiba hardware (i.e. not a PC card), the ppp daemon gets very confused when you try to establish a network connection through the modem card. It dies immediately unless you explicitly disable the eth0 interface before dialling:
(su root) $ /sbin/ifdown eth0
This is a real pain, and I have mitigated it slightly by establishing 3 different networking profiles, one for home, one for office, and one for "remote" when I am not ethernet-connected. In RH7.3, the relevant file is /etc/sysconfig/network - for dial-up access you will need to change 2 lines:
GATEWAY=0.0.0.0 GATEWAYDEV="ppp0"
For Ethernet connection to your home or office network, the lines should show the IP address of your default gateway, and "eth0", respectively.
You may like to try my shell script for switching network configurations between home-office-remote(dialup), but please follow the README first.