USB 2.0 to 4 Port RS-232 Serial Adapter Optical isolated

USB to RS232 Serial Adapter

USB 2.0 Serial Adapter with Optical isolation and surge protection is available on each serial port and is individually optically isolated with 2000 volt DC optical isolation on 8 signal pins. Meets the highest level of optical isolation protecting your computer from spikes and surges.

  • Incorporates Optical Isolation and Surge Protection over each port.
  • Connects to a Host USB system port or USB Hub via USB cable
  • Provides high speed serial port baud rate at 921.6Kbps
  • Installed as a standard Windows COM port to communicate with Factory Automation, Bar Code Scanners, Time Clocks or other.


Not in stock - Backorder allowed

Volume Pricing

Units Discount Price
1 - 4 $274.95
5 - 11 3 % $266.70
12 - 24 5 % $261.20
25 - 49 7 % $255.70
50+ 10 % $247.46

Also available from:

Model No. USB2-4COM-SI-M


This USB 2.0 Serial Adapter is designed with Optical Isolation and Surge Protection with an industrial-grade metal chassis to make and keep serial port expansion safe for your devices. The USB2-4COM-SI-M can connect to a USB port or USB hub to instantly add 4 serial communication ports to your system. The 4-Port USB 2.0 Serial Adapter makes it easy to add serial port and serial device to your system with easy plug-and-play and hot plug features and adapts easily to new technology.

USB 2.0 to 4 Port Industrial RS232 Serial Adapter

There are no IRQ & COM port conflicts, since the port doesn’t require any additional IRQ, DMA, memory as resources on the system. The RS-232 port functions as native Windows COM port, and it is compatible with Windows serial communication applications. Each port is individually configurable.

The USB 2.0 4 Port Serial Adapter with Metal Chassis provides instant connectivity to RS-232 communication devices for factory automation equipment, multi-drop data collection devices, bar code readers, time clocks, scales, data entry terminal and serial communication in harsh environment and is suitable for remote access applications requiring high speed RS-232 communication ports.

USB 2.0 RS232 4-Port Serial Features:

  • Adds 4 industrial RS-232 serial ports with optical isolation by connecting to a USB port
  • 2000V DC optical isolation
  • 25KV ESD surge protection
  • SECC metal chassis with DIN rail bracket
  • 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
  • 128 byte transmit FIFO & 384 byte receive FIFO
  • Non-standard baud rates supported
  • Installed as standard Windows COM port
  • LEDs for Power, TxD and RxD for easy port monitoring and diagnostics
  • Serial port protected with surge protection of 25KV
  • Terminal power adapter of 5V, 2A provided
  • 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
  • Supports Windows 10, 8, Windows 7, Vista, 2003, XP, 2000 and Linux
  • Item Dimensions: 6.747(L) x 3.759(W)) x 1.182in(H)

Optical Isolation and Surge Protection

Your computer is well protected, since the surges and spikes cannot cross the optical link. Each serial port is individually protected by surge protector to withstand electrostatic discharge and power surges up to 25KV ESD (Electro-Static Discharge_. Surge suppression on all signals prevent from damages caused by lightning or high voltage.

Surge protection happens by converting the electrical pulse into an optical signal and then changing it back into an electrical pulse

OS Support:

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

Package Contents

  • 4 port optically isolated USB to Serial adapter
  • USB A to B cable
  • Din Rail mounting plates and screws
  • 5V 2A output power adapter
  • Driver Disc

*Surface Mounting screws not included.


Product Specifications

Country of Origin




Physical Characteristics


Mounting Style

Din-Rail (Optional Bracket)


4 Serial Ports

Screw Lock Compatible


Serial Attributes
Serial Standards


OS Support

Linux, Win 10, Win 7, Win 8, Win Vista, Win XP

Operating Temperature

0C to 55C



Performance & Safety
Isolated/Surge Protected


Other Data

DB9 Male w/ Nuts

Chip Model



3.0 lbs

UPC: 729440690786
Compliance USB 1.1/2.0 compatible
Speed 480 Mbps, hi-speed USB
FIFO 128 byte transmit FIFO
384 receive FIFO
Serial Interface
Port Type RS-232
Number of Ports 4
Connectors DB9 male
Serial Line Protection
ESD Protection 25KV
Optical Isolation 2000V DC
Serial Port Speed
Baudrate 300 bps to 921.6k bps
Serial Communication Parameters
Data Bits 5, 6, 7, 8
Stop Bits 1, 1.5, 2
Parity None, Even, Odd, Space, Mark
Flow Control RTS/CTS, XON/XOFF
Serial Signals
Driver Support
OS Windows 7, Vista, 2003, XP (WHQL certified) and 2000
Linux Kernel and up built-in support
Power Supply
Input Self-powered
Power adapter of 5VDC, 2A
Chassis SECC metal chassis with DIN rail bracket
Operating Temperature 0 to 55 °C (32 to 131 °F)
Operating Humidity 5 to 95% RH
Storage Temperature -20 to 75 °C (-4 to 167 °F)
Safety Approvals EN55022 Class B, EN55024, EN61000-3-2, EN61000-3
IEC 61000-4-2, IEC 61000-4-3, IEC 61000-4-4, IEC 61000-4-5,
IEC 61000-4-6, IEC 61000-4-8, IEC 61000-4-11.
CISPR PUB. 22 and FCC Part 15 Class B.


RS-232 DB9 Male

RS-232 DB9 Male Connector Pin-outs

RS-232 Signal Pin-outs of DB-9 Male

RS-232 DB9 Male Connector Pin-out
  Pin Signal  
  1 DCD  
  2 RxD  
  3 TxD  
  4 DTR  
  5 GND  
  6 DSR  
  7 RTS  
  8 CTS  
  9 RI  
Optional Accessories

Optional Accessories

The USB 2.0 4 port optically isolated serial adapter has certain accessories that work with it. These accessories are what you can order if needed.

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 (0)


There are no reviews yet.

Be the first to review “USB 2.0 to 4 Port RS-232 Serial Adapter Optical isolated”