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Review: DriverGenius 4XRS232 4 Port USB to DB9 RS232 Serial Adapter Hub
Serial Hub | Connect Serial Devices to Ethernet
4-Port USB to RS-232 DB9 Serial Adapter w/ Prolific Chipset
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Startech USB to RS232/RS485/RS422 8 Port Serial Hub Adapter - Industrial Metal U 65030878579 | eBay
Renkforce RF-19"-USB2-RS232-8 8 + 2 ports Serial hub meets industrial requirements, Steel casing Black | Conrad.com