Quatech 4 Port RS-232/422/485 Serial Hub - 4 x RS-232/422/485 Serial USB 2.0

This product works well, but you should be aware of a few things. The pin map for the RS-422 interface is different from manufacturer to manufacturer, so if you choose Quatech, try to stay with Quatech, versus RocketPort. Also there are differences with A/B lead interpretation in RS-422 mode versus RS-232 mode from manufacturer to manufacturer, so be consistent in order to avoid physical pin swaps when changing modes. I believe the problem has been fixed using a firmware upgrade, but this unit will prevent a Dell PC from booting if the USB cable is plugged in prior to PC power up. I feel this is an error on the part of both Dell and Quatech, and is a problem when we do over-weekend testing and the PC doesn't reboot after a power glitch. That said, we use lots of these units here for software development and run them at high speed RS-422. Other manufacturer's units had trouble dropping characters in high speed RS-422 mode. Cheers.