USB to Edgeport/4/DB-25 RS232 .... hàng USA chuyên dụng cho tự động hoá ... bán giá 1tr.

Link tham khảo:
http://www.cnet.com/products/digi-edgeport-4-serial-adapter-series/
http://www.digi.com/products/usb-and-serial-connectivity/usb-over-serial-hubs/edgeport#partnumbers