Most of the Okidatas from the period (Microline 320, 520, etc.) had a standard Parallel port built in on the back of the printer. Right next to it is usually a plastic knockout. If you get the RS232 serial port option for this printer, you remove the plastic knockout, and slide the RS232 board into the opening. There is a card-edge connector that it mates with. You don't have to set any switches to use it. I don't really know if it will let you do "dual porting" or not. (i.e., 2 computers printing to it, one via serial, one via parallel.) As for the RJ45 adapter; those are fairly common. The serial port probably only needs 3 pins for printing, Ground, TXD, and RXD . . (7, 2, and 3), although they may have included handshaking signals. Who knows. A standard serial cable to/from your computer should work, as well as a parallel cable. Documentation should be readily downloadable As info. . . . T