Black Box LES920A-SFP-TB 4-Port Industrial Serial Device Server

Overview

The Black Box LES920A-SFP-TB is a 4-port industrial serial device server engineered to bridge RS-232, RS-422, and RS-485 legacy serial devices onto an IP network — a straightforward conversion path when you need to extend or integrate serial-based equipment without replacing hardware that still works. The SFP fiber uplink slot distinguishes this model from copper-uplink variants, giving you the ability to run fiber back to a core switch when distance or noise immunity rules out copper.

Black Box's industrial device server line is built for environments where standard commercial-grade networking gear doesn't belong — think manufacturing floors, utility substations, transportation control rooms, or building automation closets where heat, vibration, and electrical noise are facts of life. The TB designation indicates terminal block connectivity for the serial ports, which is the correct choice for permanent hard-wired installations where RJ45 patch-style connectors aren't practical.

Key Features

• 4 independent serial ports (RS-232/422/485): each port configures independently, so you can mix serial device types on a single unit rather than deploying separate converters per protocol. Reduces cabinet density and power draw in multi-protocol installations.
• SFP fiber uplink: the open SFP slot lets you choose the fiber type — single-mode or multimode — based on your actual run distance. Copper uplinks top out at 100m; fiber takes you kilometers, which matters in large campuses or extended industrial facilities.
• Terminal block serial connectors: screw-down terminals hold wire under vibration where RJ45 connectors can work loose. The right connector type for permanent, high-reliability installs.
• RS-485 multi-drop support: RS-485's bus topology lets a single port address multiple devices on one wire run — common in building automation (BACnet, Modbus) and access control wiring architectures.

Integration & Compatibility

The LES920A-SFP-TB (often searched as LES920A SFP TB) is designed to integrate with any IP network infrastructure that can accept an Ethernet uplink. Serial device servers of this class typically present each serial port as a virtual COM port or raw TCP/UDP socket to the host system — confirm your SCADA, VMS, or automation software supports the connection method before deploying. For network switch pairing, select a switch with an open SFP port matching the fiber module you install in this unit. Consult the Black Box networking product line for compatible fiber modules and complementary edge networking hardware.

Frequently Asked Questions

Q: What serial protocols does the LES920A-SFP-TB support?

A: The LES920A-SFP-TB supports RS-232, RS-422, and RS-485 serial protocols across its 4 ports, configurable independently per port.

Q: What type of fiber uplink does the LES920A-SFP-TB use?

A: It uses an SFP (Small Form-factor Pluggable) slot, allowing you to insert a fiber module — single-mode or multimode — to match your specific cable plant and distance requirements.

Q: Why does the LES920A-SFP-TB use terminal block connectors instead of RJ45 on the serial ports?

A: Terminal block (TB) connectors provide a screw-down wire termination that is more secure under vibration and in permanent industrial wiring installations compared to push-in patch connectors.

Q: Can the LES920A-SFP-TB support RS-485 multi-drop bus wiring?

A: Yes. RS-485 is inherently a multi-drop protocol, allowing multiple devices to share a single serial bus — useful for Modbus RTU, BACnet MS/TP, and similar building automation or industrial control applications.

Eden Phillips

The LES920A-SFP-TB is the model to reach for when you have legacy RS-232, RS-422, or RS-485 serial devices that need to live on a modern IP network and a copper uplink won't cover the distance back to your switch. The open SFP slot is the key differentiator — it means you're not locked into a vendor-bundled fiber module; you pick the transceiver that matches your fiber type and span.

Technical Highlights:

• 4-port multi-protocol serial: RS-232, RS-422, and RS-485 all on one unit with per-port configuration — eliminates the need for separate protocol converters when your device mix is heterogeneous.
• SFP fiber uplink: breaks the 100m copper ceiling; choose single-mode for multi-kilometer runs or multimode for shorter in-building fiber infrastructure — one hardware platform, multiple deployment distances.
• Terminal block serial termination: screw-down wiring is vibration-resistant and permanent — standard practice in industrial panels and IDF/MDF enclosures where patch connectors don't belong.

Deployment Considerations:

• Confirm the SFP module type before ordering — the unit ships with the SFP slot empty in some configurations; verify whether a module is included or must be sourced separately to match your fiber plant.
• RS-485 bus wiring requires attention to termination resistors and biasing at the physical layer — the device server handles the IP side, but improper RS-485 bus termination at the field wiring level will cause communication errors regardless of the unit's configuration.

This unit fits well in building automation and industrial control projects where Modbus RTU or BACnet MS/TP serial devices need to reach an IP-based SCADA or BMS system over existing fiber infrastructure — a cleaner integration path than running new copper over long distances.