A standard external US Robotics modem comes with a power supply and a line cord. A DB25 cable will be required. For an Option 11 system a null modem will also be needed. It's always a good idea to head to the phone room with a handful of cables and adapters. Check to make sure the TTY is enabled and working. I usually hook up with my laptop to the TTY first to check connectivity and then proceed with hooking up the modem afterwards.
Programming the modem is straightforward and only takes a couple of minutes. Unbox the modem and check the dip switches first. You need to set it so that 1, 3, and 7, are down and the rest are up. Connect the modem to your PC using a serial cable and power it on. Using your favourite terminal program (I usually use Procomm for this but Putty would also work) set to 9600/N/8/1 check to see that the modem is responding. Enter AT and press enter, the modem should respond with OK. If you don't see OK try throwing a null modem adapter in the mix and test again. Once you have a response from the modem you can enter the configuration command:
The modem should once again respond with OK. Once this is done power down the modem and change the DIP switch settings again. At this point you need to have 1 and 4 down, the rest up. Plug the modem into the TTY port and test. The modem should answer. If you don't see and output on the TTY then you may need to either add or remove a null modem to get everything working.