When I used a switchbox with my Epson 800, I tried two standard serial print cables- the printer would not work. I called Belkin, and they said I needed to use the special Belkin "throughput" cable model number ?????-???-?????, from my mac to the switchbox. I bought the cable, and although it looked the same as a print cable, my printer and modem worked. You can find the correct cabling, or at least the Belkin hotline on the box. Hope this helps, Graham Graham Johnson Medical Illustrator The Salk Institute La Jolla, CA