Broadcom modems used on Dell computers are winmodems. There may be drivers available on www.linmodems.org
that may work with your broadcom modem. If that doesn't work, your options may be limited since the 1100 doesn't have a serial port. As a matter of fact, the 1100, 5100, and 5150 series do not have parallel or serial ports but the 300m, 600m and 8600 do.