Stand-alone 10 Gigabit Ethernet Media Converter
10GBase-T Copper to Fiber

The S4120 is a stand-alone media converter that provides an interface between 10GBase-T ports and 10GBase-X slot via an open SFP+ port, allowing users to convert their 10Gig Ethernet ports to the preferred type of cabling used in their networks. The open SFP+ slot supports a wide variety of Transition Networks 10GE SFP+ fiber modules. Operating at Layer 1, the physical layer, data is passed through the converter at line speed, making the S4120 ideal for applications where low latency is essential. The ION S4120 can be managed, in-band, over the fiber, when it is linked back to a C4120 card installed in a managed ION chassis.

NDAA Compliant

S4120-1048 Overview


  • Transparent Link Pass Through
  • Auto-Negotiation
  • Auto-MDI/MDIX
  • Automatic Link Restoration
  • Loopback on Fiber and Copper
  • DMI
  • Support Remote In-band Management and Remote Firmware Upgrade when linked to a C4120 card installed in a managed ION chassis
  • Fiber Port supported standards
    • 10GBase-SR
    • 10GBase-LRM
    • 10GBase-LR
    • 10GBase-ER
    • 10GBase-ZR
  • The open SFP+ port also supports:
    • Direct attached 10G copper cable assemblies:
    • Both Class-I and Class-II fiber
    • SFP+ modules
    • SFP modules supporting WDM technology
  • Support 100m on Cat6a or higher UTP Per Energy Efficient Ethernet standards, IEEE 802.3az, UTP cable length is detected and power is adjusted according, to reduce power consumption on shorter UTP cable installs

S4120-1048 Tech Specs


  • IEEE 802.3
  • IEEE 802.3an
  • IEEE 802.3ae
  • IEEE 802.3az

Data Rate

  • 10 Gbps

Dip Switch

  • SW1: Copper Loopback
  • SW2: Fiber Loopback
  • SW3: not used
  • SW4: Transparent Link Pass Through

Status LEDs

  • PWR (Power): On = power is on
  • L/A SFP+ (Fiber port link and activity statue): On = Link OK, Flashing = Link and Activity OK
  • Copper Link (Copper Link Status): On = Link OK
  • Copper Act (Copper Link Activity): On = Activity OK


  • Width: 3.25” [82.55 mm]
  • Depth: 6.5” [165 mm]
  • Height: 1″ [25.4 mm]

Power Consumption

  • 10.5 Watts

Power Supply

  • External AC/DC power supply, Universal AC input,
  • 12VDC 1.6A output


  • Operating: 0°C to 50°C
  • Storage: -15°C to 65°C
  • Humidity: 5% to 95% (non-condensing)
  • Altitude: 0 – 10,000 ft.


  • 2 lbs. [0.90 kg]


  • With Power Supply:
    Greater than 41,660 hours (MIL-HDBK-217F)
    Greater than 114,580 hours (Bellcore)
  • Without Power Supply:
    Greater than 250,000 hours (MIL-HDBK-217F)
    Greater than 687,000 hours (Bellcore)


  • FCC Class A, EN55022 Class A, EN55024, CE Mark


  • Lifetime

S4120-1048 Downloads

Additional Product Information

Note: Some Documentation may have Transition Networks named or pictured. Transition Networks was acquired by Lantronix in August 2021. Learn more about the acquisition here.

Visio Stencils

Plan your network with Microsoft Visio Stencils. You must log in or create a MyLantronix account to access Visio Stencils.

Firmware Downloads

Keep your products up to date by downloading the latest firmware. You must log in or create a MyLantronix account to download firmware. 

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