Product Detail For ML320, ML321, ML520, ML521, ML590, and ML591 printers High-speed interface Attaches to DEC, Unisys, Altos, and other popular host systems 19,200 bps transfer rate Easy to install; uses standard ready/busy and on/off protocols . The "Okidata RS-232C Super-Speed Interface for Ml Series Serial" is best product for you. We recommended Okidata RS-232C Super-Speed Interface for Ml Series Serial