USB-4604BM
4-port Serial to USB Converter with ESD Surge Protection
Main Features
Full compliance with USB V1.1 and V2.0 specifications.
RS-232/422/485 port supported
Transmission speed up to 921.6 kbps
Automatic RS-485 data flow control
Bus-powered; no need for external power supply
Plug & Play installation
No additional IRQs or I/O ports required
Hot swap function supported
http://www.advantech.com/products/USB-4604BM/mod_086D3201-2305-4B3B-B9E1-6E316D59A9AA.aspx