4 Port USB to DB9 RS232 Serial Adapter - Serial Cards & Adapters, Add-on Cards & Peripherals

4XRS232 Industrial 4 Port USB to DB9 RS232 Serial Adapter Hub

StarTech.com 4 Port PCI RS232 Serial adapter card - PCI - serial - 4 ports - The Office Point

USB to RS485 adapters (HIGH SPEED) — Connective Peripherals - Global Store

USB 4-Port Serial Adapter / USB 2.0 Quad Port Serial DB-9 RS-232

4 Port ExpressCard RS232 Serial Card - Serial Cards & Adapters, Add-on Cards & Peripherals

4XRS232-D 4-Port USB to DB9 RS232 Serial Adapter,Add-on Cards & Peripherals,RS-232C Adapters

4-port PCI Express RS232 Serial Adapter Card - PCIe RS232 Serial Host Controller Card - PCIe to Serial DB9 - 16950 UART - Low Profile Expansion Card - Windows/Linux - BCI Imaging Supplies

StarTech.com Motherboard Serial Port - Internal - 1 Port - Bus Powered - FTDI USB to Serial Adapter - USB to RS232 Adapter - Add an RS232 serial port to any system

This PCI Express serial card adds 16 high-speed RS232 ports to your standard or low-profile desktop or server PC. This lets you maximize the number of available DB9 RS232 ports that are available for connecting your serial-based devices and equipment, while using only a single PCI Express (PCIe) slot. It's the perfect solution for adding the serial ports you need, even if your desktop PC or server only has a limited number of PCIe expansion slots.

StarTech.com 16-Port Low-Profile Serial Card - RS232 - PCI Express PEX16S550LP