The CP-134U and CP-134U-I 4-port universal PCI boards are designed for industrial automation applications that require a long distance, multi-point, PC-based data acquisition solution. On-chip Automatic Data Direction Control for precision RS-485 communication RS-485 communication requires precise timing control to enable and disable the line driver. The Moxa Turbo Serial Engine chip that powers the CP-134U board comes with on-chip ADDC, which makes RS-485 as easy to use as RS-232. RS-485 multidrop for up to 31 devices within 1.2 km The CP-134U universal PCI board has 4 RS-422/485 serial ports, each of which can achieve data rates up to 921.6 Kbps. In RS-485 mode, the board can connect up to 31 daisy-chained RS-485 devices within a range of 1.2 km. For long distance RS-485 communication, choose the CP-134U-I, which comes with 2 KV optical isolation protection to prevent equipment damage.