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Thomas Supplier


 QSU-200/300 - OBSOLETE

See the QSU2 and DSU2 Series which replace the QSU

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 4 port USB to RS-422/485 serial adapter 

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US Prices
CDN Prices

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  • 2,4,8 or 16 independent ports
  • Each port configurable for RS-422 or RS-485
  • Device enumerates itself as standard ports
  • Max baud rate 460.8k bps
  • Full-duplex or half-duplex modes
  • Surge suppression available
  • Bus powered, no external power required
  • 5 year warranty


Quatech USB to RS-422/485 serial adapters are easily configured to enable the continued use of legacy devices without making any changes to the applications written for them. The adapters enumerate themselves as standard COM ports making the USB interface completely transparent to software. The ports can be configured as RS-422 or RS-485 in any combination, meaning a single adapter can be used to implement multiple full-duplex and half-duplex multi-drop networks.

Implementing RS-422/485 serial devices via USB provides many advantages. It enables "plug & play" capability as well as hot-swapping. And, while in standard systems each serial port requires a separate port on the PC, with Quatech adapters a single USB port can be used to implement 8 serial ports or up to 80 RS-422 or 256 RS-485 devices. In addition, Quatech USB to serial adapters contain deep data FIFOs and use an accelerated UART clock frequency to further boost data rates. A single port on the adapter can typically achieve 230.4k bps data rates, and under certain conditions may be capable of up to 460.8kbps



USA Office

Address: 1480 Gulf Road, Suite 837,
PO Box 1364
Point Roberts, WA 98281

Western Canada - Vancouver BC

Tel:1.800.663.6001 or 1.604.925.6150
Address: 2454 Haywood Ave
West Vancouver, BC V7V 1Y1

Eastern Canada - Markham, Ontario

Tel:1.800.465.0164 or 1.905.513.7027