Yes, you can use up to 8 AMT8's or Unitor8's on Macintosh and Windows PCs. Basically you can chain the opposing serial ports together (i.e. if you hook the 1st AMT8 or Unitor8 to PC via RS232 serial port, you can chain the next AMT8/Unitor8 with the RS422 port, and then the next one via the RS232 port and so forth.) A more descriptive example is provided in the manual.