4-Port USB DB-9 Serial Adapter Solution

USB to RS232 Cable Windows 11

The USBG-4X2FTDI 4-Port USB DB-9 Serial Adapter is a rugged plastic USB to Serial adapter that allows you to add 4 RS-232 serial ports to your computer by connecting to a single available USB port. There are no IRQ & COM port conflicts during install.

  • USB host extends to 4 USB to RS232 5ft. cable ports giving additional COM’s to work with.
  • Installs as a standard Windows COM port with no system conflicts.
  • Takes advantage of High-Speed communication with FTDI Drivers.
  • DB9 Male serial ports connectors have screw lock security for safe connections.


(20 customer reviews)

In stock

Volume Pricing

Units Discount Price
1 - 4 $76.95
5 - 11 3 % $74.64
12 - 24 5 % $73.10
25 - 49 7 % $71.56
50+ 10 % $69.26

Also available from:

Model No. USBG-4X2FTDI

Software & Drivers

Quick Links:


The USBG-4X2FTDI 4-Port USB DB-9 Serial Adapter is designed to make serial port expansion as easy as possible with its Windows 11 support. Connecting to a USB port on your computer or USB hub, the USB Quad Serial Adapter instantly adds four RS-232 serial communication ports to your system. By taking advantage of the USB Bus, the 4-Port USB DB-9 Serial Adapter installation of serial ports and devices to your system painless with both Plug-and-Play and hot plug features.

Gearmo 4 port serial adapter cable with disc

Plugging the USB Quad Serial Adapter to the USB port, the adapter is automatically detected and installed. There are no IRQ & COM port conflicts, since the ports do not require any additional IRQ, DMA, memory as resources on the system. The USB Quad Serial Adapter is self-powered and does not require any external power adapters.

4-Port USB DB-9 Serial Adapter open case image

The 4-Port USB DB-9 Serial Adapter provides instant connectivity with modems, ISDN TAs, PDAs, handheld & pocket PCs, digital cameras, POS, serial printers. It is suitable for remote access, retail and industrial applications, data collection and other applications requiring high speed RS-232 serial communication ports.


Additional Features:

  • Adds four RS-232 DB9 serial ports by connecting to a Single USB port
  • Rugged plastic housing with built-in LED status indicators for TxD and RxD
  • Installed as standard Windows COM port
  • Full RS-232 modem control signals and hardware/software flow control
  • RS-232 data signals: TxD, RxD, RTS, CTS, DSR, DTR, DCD, RI, GND
  • High speed serial port with the baud rate up to 921.6K bps
  • Non-standard baudrates supported
  • Serial port protected with surge protection of 10KV
  • Powered by USB port, no external power adapter required
  • Easy plug and play installation and RS-232 device connection
  • COM port number assigned can be changed to any COM port number required
  • Works with USB 1.1 & 2.0 host port
  • 5ft long total length
  • Windows 11 support with FTDI

OS Support:

  • Windows 11, 10, 8, 7
  • Linux and Mac OS 10.X

Package Contents

  • 4-Port USB DB-9 Serial Adapter
  • Driver Disc

Product Specifications

Operating Temperature

0°C to 55°C (32°F to 131°F)

Storage Temperature

-20 to 75°C (-4 to 167°F)


5% ~ 95% (non-condensing)



LED Indicators

Power, TX / RX

Product Information

1 year from date of purchase

OS Support

Win 11, Linux, Mac OSX, Win 10, Win 7, Win 8

Serial Attributes
RS Signals


Serial Standards


Baud Rate

921.6K bps

FIFO Receive

384 bytes

FIFO Transmit

128 bytes

Data Bits

5, 6, 7, 8


None, Even, Odd, Mark, Space

Stop Bits

1, 1.5, 2

Flow Control

Hardware (RTS, CTS), XON/XOFF

USB Type

USB 2.0

Screw Lock Compatible







4 Serial Ports

Material of Construction


Country of Origin


Other Data

DB9 Male with Screws


1 year from date of purchase


.6 lbs


7 × 5.25 × 1.5 in

UPC: 729440691981

DB9 RS-232 Pin-Outs

DB9 RS-232 Pin-Out Diagram
DB9 RS-232 Pin-Out Chart

Optional Accessories

Optional Accessories

The 4-Port USB DB-9 Serial Adapter has certain accessories that work with it. These accessories are what you can order if needed.

RS232 Male to Female Serial Data Cable Complete your serial data connection with this 5ft. RS232 DB-9 Male to Female data cable for fast reliable…

Model# 9DBMF5FT


In stock


Product Documentation & Drivers

Software & Drivers

Need drawings, CAD files, or other compliance documentation? Click HERE

Serial F.A.Q.

Product F.A.Q.

View frequently asked product questions below. For all serial troubleshooting, visit this page.
Still need help? Reach out!

  • How do I clean and reinstall my FTDI drivers?
      1. Download the CDM Uninstaller HERE.
      2. Extract the zip file, or open the “CDMuninstallerGUI.exe” utility.
      3. Leave the ‘Vendor ID’ set to 0403 and ‘Product ID’ set to 6001.
      4. Click Add.
      5. Click Remove Devices.
      6. Download the corresponding driver for your operating system and follow on-screen prompts. Windows Driver | MacOS Driver

    Video tutorial here.

  • How can I change my device’s COM port?
      1. Click on Start and navigate to the Control Panel
      2. Locate and click on Device Manager
      3. Under “Ports (COM & LPT)” you will find your serial device titled “USB Serial Port” along with its current COM Port.
      4. Right click on “USB Serial Port” and click on Properties.
      5. Navigate to the “Port Settings” tab and click on “Advanced…”
      6. Once there, the “COM Port Number:” can be changed with a dropdown menu to select the port number.
      7. Click your desired port number (i.e. COM2) and click “OK”.
      8. Click “OK” once more.
      9. Your serial device is now assigned to your chosen COM Port.


  • How do I check to ensure the COM port is listed properly in Windows?
    To ensure your serial device is installed properly, complete the following:

    1. Press Windows Key + R to open the Device Manager. Once Run comes up, type “devmgmt.msc” into the text field and press Enter.
    2. Expand the section labeled, Ports (COM & LPT).
    3. You should now see a COM number in brackets to the right of each port. If the device is installed properly, no exclamation points or question marks should be present next to the device.
  • I have everything hooked up, but nothing is functioning correctly.
    To rule out potential issues, quickly test your individual components to ensure that they are working correctly individually, and are not the source of the problem:

    • Serial cables
    • Serial ports
    • Serial devices

    Test your components by:

    • Hook up the serial cable(s), serial port(s), and serial device(s) in a different setup to see if the issue stems from a particular component, or the setup as a whole.
    • Replace the serial cable, port, or device within your setup to further troubleshoot the issue’s origin.

    When testing cables:

    • Test each cable individually.
    • Use short cables when you are testing.

    When testing serial ports and devices:

    • Press the Windows key + R, in Run, type devmgmt.msc, and press Enter to open the Device Manager. You can then check to see if your device is listed under Ports (COM & LPT).
    • Ensure 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.
  • Serial communication is not functioning correctly, how can I tell if the problem caused by the adapter or my serial software application?
    Older serial communication applications make use of legacy hardware addresses, often incompatible with PCI, PCIe, and USB to Serial products. Contact the software provider to troubleshoot.
  • I am receiving an error when I try to install the drivers in Windows 8 64 bit.
    Driver Signature Enforcement in Windows 8 may need to be disabled in order to use various drivers. After disabling this feature, the driver will be allowed to install.

    Note: You are required to restart your computer after disabling the Driver Signature Enforcement. Save all open work on your computer.

    Disable driver signature enforcement:

    1. Press the Windows key + C.
    2. Click Settings > Change PC Settings.
    3. In the left pane, click General.
    4. In the right pane, under Advanced startup, click Restart now.

    When your system restarts:

    1. Click Troubleshoot > Advanced options > Startup Settings > Restart.
    2. Press 7.

    When your computer restarts, Driver Signature Enforcement will be disabled and you can install the drivers.

  • I am receiving an error when I try to install the drivers in Windows 10 64 bit.
    Driver Signature Enforcement in Windows 10 may need to be disabled in order to use various drivers. After disabling this feature, the driver will be allowed to install.

    Note: You are required to restart your computer after disabling the Driver Signature Enforcement. Save all open work on your computer.

    Disable Driver Signature Enforcement:

    1. Click the Windows icon in the taskbar.
    2. Click Power.
    3. Press and hold the Shift key and click Restart.

    After your computer restarts:

    1. Click Troubleshoot Advanced Options Startup Settings Restart.
    2. Press 7.

    When your computer restarts, Driver Signature Enforcement will be disabled and you can install the drivers.

  • Why did the software not install properly in macOS High Sierra (10.13) or later?
    High Sierra 10.13 and later versions of macOS enforce strict security policy revisions. In order for the device to operate, software packages like those used in this installation must be allowed in macOS Security and Privacy settings once the software is installed.

    Once the driver/software is installed, follow these steps to allow the software:

    1. Open System Preferences.
    2. Open Security & Privacy.
    3. Click the Allow button near the bottom of the General tab.
Reviews (20)

20 reviews for 4-Port USB DB-9 Serial Adapter Solution

  1. Michael Accardi

    5.0 out of 5 stars

    Great product!!!!
    I recently purchased two Gearmo 4 Port USB to Serial RS232 Adapters to set up a console server for managing my Cisco network lab, and I must say, I’m absolutely thrilled with their performance! These adapters are connected to a single Raspberry Pi 4, and the setup was a breeze. The installation process was straightforward, and I encountered no issues getting them up and running.What impresses me the most is the seamless integration and ease of use. The adapters are highly reliable, providing consistent and fast data transfers, which is crucial when managing a network lab. I’ve experienced zero lag or connectivity issues, making my lab management tasks significantly more efficient.The build quality is excellent, and the adapters are compact enough not to clutter my workspace. They’ve proven to be an invaluable addition to my setup, and I couldn’t be happier with how well they’ve met my needs. If you’re in the market for a reliable and high-performing USB to Serial adapter, look no further than the Gearmo 4 Port model. It’s a game-changer!

  2. handy

    Works with Mac mini M2 Pro
    Plug and Play out of the box. No drivers to install. Mac mini M2 Pro.

  3. Gotallofthem “Speed Demon”

    I have a home lab that I have built for my Networking Studies, and I needed a way to access each switch/router without having to constantly plug and unplug my console cable each time I needed to make changes (which is really annoying if you know what I am referring to). My choice was between buying an access server which would have cost me a lot more, or purchasing this item. I must say this has done the job perfectly, I can control 4 different units, with one connection, and not having to constantly get up out of my seat. If you have a home lab, or you need a way to access your switches and routers at the same time, at home/work, this will work great for you.

  4. JohnG

    Most of the inexpensive serial to RS-232 converters have been bricked (made unusable) by an update to windows 7 and 8 by Prolific(FTDI) in order to punish counterfeiters of their chips and I can understand that. However, it leaves people like me with
    devices that are worthless! I have several converters from GearMo that have seemed to survive. Don’t know if it is the drivers they send or if they are using legitimate FTDI chips. The bottom line is that so far they work fine and are well built. I know for sure that the little blue converters and a lot of cheep ARDUINO boards suffer problems from the update. There is a somewhat involved workaround to fix the problem but I don’t know if it is worth it. Could be that another update from Prolific could render the fake ones inoperable again. Bottom line….. Pay a little more, buy from Amazon and one way or another your problems will be taken care of.

  5. Ian

    Nothing comes close to the value. I’ve connected this to a raspberry pi in order to use it as a terminal server for my cisco lab equipment. I will be buying another one of these in the near future. I love that the connectors are numbered and that the cables are of a good length

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