External modems (thats what a 5630 is if I followed that link correctly) are a cakewalk to set up, just make sure the com port you plugged it into is enabled in the BIOS, I've forgotten that before
Oh and there are no 'drivers' needed since your modem isn't one of those gimpy software modems where they leave chips out and make up for it with software, all it needs to do is talk to the com port it's plugged into which Linux knows how to do.
Type 'ls -l /dev/modem' to see where /dev/modem actually points to. External modems usually go into one of the motherboard's com ports so it should be ttyS0 or ttyS1. You can also try your echo command to /dev/ttyS0 or /dev/ttyS1 instead of /dev/modem, one of those should get lights to flash on the modem at least.