You plug a USB cable in between the computer and SmoothStepper. Ports 1&2 on the SmoothStepper are deigned to be Pin by Pin compatible with a standard parallel port, you use the LPH26 to DB25 cable to convert the SmoothStepper 26 pin header sockets into a regular parallel port cable connector. There is a driver and Mach plug-in that you install.