Keyspan USA-28x External USB to Serial Adapter When the iMac and Macintosh computer systems decided to go with the USB interface port over the old serial port, some Mac owners were a little upset. Previous Mac computers had serial ports for printers and other peripherals The USA-28X from Keyspan fits into one USB port and provides 2 serial interface ports to enable use of your original Mac peripherals Easily plugs into a USB port on an iMac, iBook, current G4 Macintosh Draws its power from the USB connection -- a power adapter is not required Provides two RS-422 mini-DIN8 ports