Ethernet to Isolated 1-Port RS-232, RS-422, RS-485 Serial Server with Opto-isolated Input and Reed Relay Output

Part: 4103   Model: SeaLINK.ULTRA


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Sealevel’s 4103 Ethernet to serial server is the easiest way to connect a single RS-232, RS-422, or RS-485 serial port to your Ethernet network. The 4103 also includes a Reed relay output and an optically isolated input to allow remote control and monitoring of real-world devices. SeaLINK® products use industry-standard RFC 2217 TCP/IP protocol for maximizing compatibility with the widest range of applications and devices.

Sealevel’s SeaLINK software drivers and utilities make installation and operation easy using Microsoft Windows operating systems. After software installation, the 4103’s serial ports appear as virtual COM ports to the host machine. Standard serial operating calls are transparently redirected to the 4103, guaranteeing compatibility with legacy serial devices and enabling backward compatibility with existing software. Serial tunneling is also supported, allowing two native serial devices to communicate over a network. Alternatively, raw data socket mode is supported, eliminating the need for a driver.

The 4103 is compatible for use with Linux; please contact Sealevel Tech Support for suggested open-source software resources.

To simplify installation and configuration, a printed copy of the SeaLINK QuickStart Guide is included with all Ethernet serial server orders.

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Additional information



Digital I/O

Isolated Inputs, Reed Relay Outputs


4.5 (L) x 4.2 (W) x 1.1 (H)

Electrical Interface

RS-232, RS-422, RS-485

Humidity Range

10 – 90% Relative Humidity, Non-Condensing

Host Interface(s)


Max Data Distance

4000 feet

Max Data Rate

230.4K bps

Optically Isolated


Operating Temperature

0°C to 70°C (32°F to 158°F)

# of Ports


Power Requirement

9-30 VDC @ 3.25W

Serial Connector(s)


Storage Temperature

-50°C to 105°C (-58°F to 221°F)

  • Ethernet 10/100BaseT (autosense)
  • Configurable as RS-232, RS-422, or RS-485
  • Serial port is optically isolated
  • Automatic RS-485 enable/disable
  • Appears as a virtual COM port to host machine
  • Data rates to 230.4K bps
  • Supports custom baud rates and 9-bit protocol
  • Reed relay output: 60VDC @ 500mA max
  • Optically isolated digital input for monitoring +5V to +24V
  • Accepts 9-30VDC power input range
  • Includes 120V AC adapter that outputs 12VDC @ 500mA (Item# TR104)
  • Includes 7′ Ethernet patch cable (Item# CA246) and 7′ Ethernet crossover cable (Item# CA251)
  • Sealevel SeaLINK software supports Microsoft Windows and Linux operating systems


Datasheet: 4103


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