The US Robotics Performance Pro 5610B is a true hardware modem,
but since it's an internal card Linux seems to have trouble configuring it at an appropriate serial port.
This utility attempts to set up the modem at /dev/ttyS3 (COM4), and then create a symlink to /dev/modem


INSTRUCTIONS  (this README is found in /root/my-applications)

## run this command to set up the modem
/root/my-applications/bin/serial start

Then configure your favourite dialler to connect to /dev/modem