The BRI4520 is not a modem. It's a BOCA VIC-1 STARTECH ASYNCH SERIAL CONTROLLER, ISA-16, 8 X R
laymans language: an 8 port (using Startech chipset) serial card built around 1993 (to fit ISA slot). A very expensive device when it was first introduce and today might bring $1.00 (on ebay) if your lucky. If you need a couple more, let me know... I can make you a good deal on them.
I'm not really sure what you want as you didn't choose an operating system in our request form and the device is not a modem. How can we help you? I doubt very seriously if you will find any support for this device in modern Windows os's.... or a very practical use for it unless you're needing multiple ansynchronous serial ports available on a single pc.