Zoom 2945 56K External Fax Modem is Zoom's classic, award-winning, external fax modem. It plugs into the serial (RS-232C) port of a Windows, Macintosh or Linux-based desktop computer. The 2945 56K External Fax Modem performance is further enhanced by its on-board controller and DSP (Digital Signal Processor). The Zoom 2945 56K External Fax Modem is capable of receiving data from an Internet Service Provider (ISP) or online service over standard phone lines at speeds up to 56 Kbps uncompressed. Outgoing data is transmitted at speeds up to 33.6 Kbps.