StarTech.com USB to Serial Hub - 8 Port - COM Port Retention - Rack Mount and Daisy Chainable - FTDI USB to RS232 Hub - Convert a USB port into 8 RS232 serial ports in an industrial rack-mountable chassis, and daisy chain multiple hubs for a scalable solution - 8-Port USB-to-Serial Adapter Hub - USB to RS232 port adapter with FTDI chipset and COM port retention
Tripp Lite 2-Port DB9 RS232 PCI Serial Adapter Card Full Profile 16550 UART - Full-height Plug-in Card - PCI - PC, Linux - 2 x Number of Serial Ports External
Tripp Lite 2-Port DB9 RS232 PCI Serial Adapter Card Low Profile 16550 UART - Low-profile Plug-in Card - PCI - PC, Linux - 2 x Number of Serial Ports External
Tripp Lite USB to Serial Adapter Converter RS-422/RS-485 USB to DB9 1-Port - External - USB Type B - PC, Mac, Linux - 1 x Number of Serial Ports External
Tripp Lite USB to Serial Adapter Converter RS-422/RS-485 USB to DB9 2-Port - External - USB Type B - Linux, Mac, PC - 2 x Number of Serial Ports External
Tripp Lite USB to Serial Adapter Converter RS-422/RS-485 USB to DB9 4-Port - External - USB Type B - PC, Mac, Linux - 4 x Number of Serial Ports External