1 Port ISA RS232 Serial Adapter Card with 16550 UART

Add an RS232 port to legacy computer systems through an ISA slot

Product ID: ISA1S550

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  • Includes drivers for Windows® 3.1, 95, 98, NT4, NT5
  • Full jumper set to ensure compatibility with almost any PC system
  • Supports the RS-232 interface

StarTech.com's ISA-based RS232 Serial Card (16550 UART) can be installed in an ISA motherboard slot to add an RS232 serial COM port, with support for data transfer rates of up to 460.8Kbps for peak serial device performance.

The ISA Serial Adapter Card includes drivers for Windows® 3.1, 95, 98, NT4 and NT5, and offers a full built-in jumper set to ensure easy configuration and broad compatibility.

A cost-effective solution for connecting serial modems, POS devices, PDAs, digital cameras, printers, ISDN terminal adapters and more, to a system, the ISA serial card is backed by StarTech.com's Lifetime Warranty and free lifetime technical support.


  • <b>Manufacturing</b> (CNC machinery, process control equipment, bar code scanners, serial printers)
  • <b>ISDN Networking</b>
  • <b>Hospitality/Restaurant</b> (credit card/debit card reader, serial printers)
  • <b>Hotel Front Desk</b> (serial printers, bar code scanners, keyboard, mouse, receipt printer, credit/debit card reader)
  • <b>Healthcare</b> (patient monitoring equipment, nurses' stations, modems)
  • <b>Environmental Control</b> (lighting, temperature, clocks)
  • <b>Casino</b> (video lottery terminals, slot machines)
  • <b>Security</b> (UPS control, access key panels, video cameras, card readers, modems)
  • <b>Consumer</b> (modems, PDAs, digital cameras, printers)
  • <b>POS</b> (credit/debit card readers, receipt printers, bar code scanners, cash registers, scales)

The StarTech.com Advantage

  • Built-in jumpers provide allow easy configuration to any free IRQ
  • Easy to install and use with full step-by-step instructions
  • Data transfer rates of up to 460.8 Kbits/sec. for peak serial device performance

Partner Numbers

  • UPC 065030781756


Warranty Information Warranty Lifetime
Connector(s) 1 - Connector Type(s) ISA (16-bit)
1 - External Ports DB-9 (9 pin, D-Sub)
Environmental Operating Temperature -10°C to 80°C (14°F to 176°F)
Storage Temperature -20°C to 100°C (-4°F to 212°F)
Humidity 5~85% RH
Hardware Ports 1
Interface Serial
Bus Type ISA
Card Type Standard Profile
Port Style Integrated on Card
Chipset ID National Semiconductor - NS16550AFN
Packaging Information Package Length 15 cm [5.9 in]
Package Width 22 mm [0.9 in]
Package Height 13.8 cm [5.4 in]
Shipping (Package) Weight 0.1 kg [0.3 lb]
Performance Maximum Data Transfer Rate 460.8 Kbps
Serial Protocol RS-232
Max Baud Rate 460.8 Kbps
FIFO 16 Bytes
General Specifications COM Settings: COM1 to COM7
Physical Characteristics Product Length 12.8 cm [5.0 in]
Product Height 7 cm [2.8 in]
What's in the Box 1 - Included in Package I/O CARD
Instruction Sheet



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Frequently Asked Questions


When you troubleshoot issues with a serial device, there are some quick tests that you can complete to rule out potential problems. You can test to make sure that the following components are working correctly and are not the source of the issue:

  • Serial cables

  • Serial ports

  • Serial devices

To test your setup components, try the following:

  • Use the serial cable, serial port, and serial device in another setup to see if the problem is with the components or the setup.

  • Use a different serial cable, serial port, and serial device in your setup to see if the problem persists. Ideally, you should test a component that you know works in another setup.

When you test your cables, it is recommended that you do the following:

  • Test each cable individually.

  • Use short cables when you are testing.

When you test the serial ports and serial device, it is recommended that you do the following:

  • Press the Windows key + R, type devmgmt.msc, and press Enter to open Device Manager. Check to see if your device is listed under Ports (COM & LPT).

  • Make sure that the COM port number is the correct number for the serial device and that the software being used to connect the computer to the serial device uses the correct COM port number. 

  • If the device is listed with an error, follow the instructions on the website to reinstall the drivers.

Note: Some serial devices work only if the COM port number is between a certain range. For example, COM1 to COM4.

To check whether or not an RS-232 serial port is working, perform an RS-232 loopback test by doing the following:

  1. If your serial port is not female, convert it by taking a female/female cable or gender changer and plugging it into the serial port.
  2. Take a metal paperclip or wire and cross pins 2 and 3. If you look closely at the female end, the pins should be numbered.
  3. Open a telnet session on the COM port number of the device that you are testing. To find out the COM port number, refer to the following FAQ: https://www.startech.com/faq/com-port-listing-windows.

Note: To open a telnet session on the COM port, you need a telnet client like PuTTY or Hyper Terminal. Windows XP comes with Hyper Terminal.

  1. When the session is open, anything you type into it you should see. The loopback test fails when you cannot see what you are typing.

If the loopback test fails, make sure that the serial cable or gender changer that you are using works and that the adapter is in the correct port. 

You can check multiple ports at the same time by opening multiple sessions, putting the loopback adapter on one port, and trying to type into each session.  When you can see what you are typing, you know that the COM port is working and you can see which port number the physical serial port is. Close the window for the port that you just tested to speed up the testing of the remaining serial ports.

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Compliance and safety

Compliance letters

Safety Measures

  • If product has an exposed circuit board, do not touch the product under power.
  • If Class 1 Laser Product. Laser radiation is present when the system is open.
  • Wiring terminations should not be made with the product and/or electric lines under power.
  • Product installation and/or mounting should be completed by a certified professional as per the local safety and building code guidelines.
  • Cables (including power and charging cables) should be placed and routed to avoid creating electric, tripping or safety hazards.
*Product appearance and specifications are subject to change without notice.

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