USB to 8-Port RS-232, RS-422, RS-485 DB9 Serial Interface Adapter

Part: 2803   Model: SeaLINK+8

(4 customer reviews)


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The SeaLINK® 2803 USB serial I/O adapter provides eight RS-232, RS-422, or RS-485 serial ports for USB connectivity to legacy or non-USB compliant devices. Each serial port can be individually configured via dipswitches located inside the enclosure.

The 2803 is housed in a rugged metal enclosure making it ideal for rugged and industrial environments. The adapter integrates Sealevel’s SeaLATCH locking USB port, which is fully compatible with standard USB cables. When used with the included USB cable with a locking type B connector, the metal thumbscrew provides a secure connection to the device and prevents accidental cable disconnection. Additionally, the high-retention type B connector helps prevent unintentional separation from a standard USB cable.

Sealevel SeaCOM USB software drivers and utilities make installation and operation easy using Microsoft Windows and Linux operating systems. After installing the software, simply plug the 2803 into an available USB port. The serial ports are recognized as standard COM ports by the host system enabling compatibility with legacy software.

All Sealevel SeaLINK USB serial adapters use a state-machine architecture that greatly reduces the host computer’s overhead when communicating over multiple serial ports simultaneously while supporting data rates to 460.8K bps. Status LEDs on the front of the enclosure indicate power and serial data activity on each port.

Standard operating temperature range is 0°C to 70°C and extended temperature range (-40°C to 85°C) is optional.

Do you know that adapter design can impact your application? Find out how in this USB Serial Performance report.


Additional information



Operating Temperature

0°C to 70°C (32°F to 158°F)

USB Powered


Storage Temperature

-50°C to 105°C (-58°F to 221°F)

Serial Connector(s)


SeaLATCH Locking USB


RoHS Compliant


Power Requirement

+5V @ 500mA

# of Ports


Max Data Rate

921.6K bps

Communications Chip


Max Data Distance

4000 feet

Host Interface(s)


Humidity Range

10 – 90% Relative Humidity, Non-Condensing

High Retention USB


Electrical Interface

RS-232, RS-422, RS-485


8.7" (L) x 6.1" (W) x 2.0" (H)

USB Specification

1.1 Compliant2.0 Compatible

  • Compliant with RoHS and WEEE directives
  • Each port individually configurable for RS-232, RS-422, or RS-485
  • High-speed UART with 128-byte Tx FIFO and 384-byte Rx FIFO
  • Data rates to 921.6K bps
  • Automatic RS-485 enable/disable
  • Serial and USB activity LEDs
  • Hot-swappable
  • Powered by USB connection
  • Sealevel’s SeaLATCH locking USB port provides secure connection with SeaLATCH USB cables via metal thumbscrews
  • Sealevel software supports Windows and Linux operating systems
  • DB-9M connectors
  • Includes 6′ USB type A to SeaLATCH USB type B device cable (Item# CA356)

Windows Software

Software: SeaCOM - Windows

Linux Software

Software: SeaCOM - Linux


Datasheet: 2803

4 reviews for SeaLINK+8

  1. Aric

    Easy integration
    I have been using this adapter for more than 3 years now and you make it so easy to read all 8 of my channels simultaneously on one computer with one cable. It has performed flawlessly in our transition from XP to Windows 7. Great product!

  2. Cowboy2020

    Sealevel 2803 Evaluation
    8 Port Sealevel Serial Switch with Manual Dip-Switches for Baud Rate… due to the increase in device input to my Computer systems, we were in need of more serial ports to the Computer… We were using the 4 Port Serial Sealevel, but did not want to just add another 4 Port and cause clutter under the Dash on the Boats… The 2803 fit that bill, and allowed for Manual control of Baud Rate, and Com Port settings that did not conflict with other devices plugged into the Computer… Software setup on Windows 7 is fast and easy… Just do not plug the Sealevel in until the software is installed, and once done, its plug and play from there. Windows will detect and assign the Com Ports for you. So far I have not had no failures out of the 18 that I have installed, and have been able to mount the boxes in very tight spaces, without the problem of over heating since it does not use that much power for the LEDs on the front as indicators…

    I would recomend the use of the Sealevel 2803 over any of the other products on the market at this time.

  3. Tugboats

    One device to connect all navigation equipment
    One of the nice things about the Sealevel SeaLINK USB serial adapter is the ability to run RS-232, RS-422 and RS-485 in one package. Most of our navigation equipment ties into Rose Point Navigation software and varies in connection standards . We are currently upgrading and standardizing our fleet of tugboats and the SeaLINK 2803 and the SeaLINK 2403 make configuring devices easier. Should a device fail, replacement is a snap. I also appreciate the technical support provided. Easy testing with tech support and quick unit replacement if there is ever a failure.

  4. Brendan C.

    SeaLevel 2803 Saves the Day! (or at least our program design)
    I was brought onto a program which had already purchased hardware to provide a USB to serial solution for rigorous system testing. Upon initial hardware integration of the overall system it was clear that the current hardware would not work. I contacted the company and was told the hardware we purchased would only work with older Operating Systems and then was steared toward a different solution that was not allowed by our customer. I was then challenged to find a new solution, my internet search returned SeaLevel, and after a few phone calls and emails I ended up with the 2803 (I was even sold an intermediary solution due to my program schedule that got our program through some initial milestones until the 2803’s were available, a huge help). In the interest of full disclosure there was a revision of the 2803 that was a little flakey, but it was soon replaced by a much more stable revision. The 2803 allows us to fully test to our customers’ satifaction. The only suggestion, but may be too specific to our situation, would be to make the DIP switches more easily accessable.

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