Component Snapshot At-a-Glance
- Model: A4H254-8F8T
- Alt. P/N: Foxboro OEM part marking P0973JP
- Product Series: Enterasys SecureStack A4 managed industrial switch platform
- Hardware Type: 1U 19-inch rack mount Layer2+ stackable all-gigabit mixed-media switch
- Key Feature: 8 fixed 1G copper RJ45 + 8 independent open SFP gigabit slots without preinstalled transceivers
- Primary Field Use: Aggregate local copper-connected controllers and long-distance fiber-linked FBM modules inside Foxboro I/A DCS process cabinets.
A4H254-8F8T
Hard-Numbers: Technical Specifications
- Protocol Support: 802.1Q VLAN, MSTP/RSTP, 802.1p QoS, LACP trunking, IGMP Snooping, SNMPv2c, basic static routing
- Port Count: 8×10/100/1000BASE-T RJ45, 8×SFP Gigabit slots, 1×RS232 DB9 console port, internal dedicated stacking channel
- Baud/Data Rate: Copper auto-negotiate 10/100/1000Mbps; SFP slots support 1000BASE-SX/LX copper/fiber transceivers
- Operating Temperature: 0°C ~ +50°C continuous cabinet operation; -40°C ~ +70°C non-operational storage
- Isolation Rating: 1500VAC galvanic isolation separating SFP port bank and core ASIC to block cabinet surge spikes
- Power Draw: Max 29.5W full-load power consumption
- Switch Fabric: 40Gbps total switching capacity; 17.86Mpps wire-speed forwarding rate
- MAC Table Depth: 16384 MAC address entries stored in onboard nonvolatile flash memory
- Input Power: Built-in universal 100–240VAC internal PSU, compatible with external C2RPS-PSM redundant backup power supply
The Real-World Problem It Solves
Separate standalone copper switches and external fiber media converters crowd limited U-space inside dense DCS rack enclosures. Extra intermediate wiring junctions increase EMI exposure near MCC feeders and lead to intermittent PV dropouts across critical control loops.
Where you’ll typically find it:
- Refinery FCC/CDU remote I/O cabinets connecting local cabinet PLC via copper and field FBM hardware via fiber uplink
- Coal-fired power boiler auxiliary DCS racks linking feedwater controllers and turbine monitoring equipment
- Outdoor chemical process instrument shelters needing flexible fiber routing to bypass CAT5 100-meter distance restriction
Consolidated mixed-port chassis cuts extra accessory hardware and lowers recurring site spare inventory overhead.
Hardware Architecture & Under-the-Hood Logic
This unit uses split-isolation dual PCB layout; SFP transceiver daughterboard is electrically decoupled from main ASIC management board to contain field-side surge damage away from core switching circuitry. It functions as edge aggregation tier between field DCS hardware and central core backbone switches.
- Inbound copper Ethernet signals from on-cabinet controllers convert via onboard RJ45 PHY chips; inserted SFP modules complete optical-to-electrical conversion for fiber feeds.
- All parsed data frames route into central switching ASIC, preconfigured Foxboro QoS rules assign highest forwarding priority to DCS interlock and Modbus TCP traffic.
- Intra-cabinet peer-to-peer traffic switches locally across internal fabric without uplink bandwidth consumption.
- Outbound long-distance backbone traffic routes out selected SFP slots or dedicated stacking ports toward core plant switches.
- Stack sync logic aligns firmware and running-config across chained A4-series switches to operate as single unified logical device.
- Onboard flash retains full startup configuration through full AC power interruptions, eliminating manual post-power-failure reprogramming.
A4H254-8F8T
Field Service Pitfalls: What Rookies Get Wrong
Improper SFP Wavelength Mismatch for Installed Field FiberNew field tech inserts single-mode LX SFPs into slots wired for multimode plant fiber. Optical mismatch creates unstable link fluctuation that worsens with cabinet ambient temperature swings.
- Quick Fix: Deploy 850nm SX multimode SFP for short-run indoor fiber; reserve 1310nm LX single-mode only for cross-site long haul trunk cabling.
Incorrect Redundant Power Supply SelectionMaintenance crew connects POE-capable C2RPS-POE instead of designated C2RPS-PSM backup PSU. Excess POE feed voltage damages internal onboard power regulation components.
- Field Rule: Restrict external redundant backup exclusively to non-POE C2RPS-PSM power modules for all A4-series switch deployments.
Live Stack Addition With Out-of-Sync Firmware VersionsTechnicians plug replacement spare switch directly into active production stack without version validation. Firmware disparity triggers stack split and renders all ports on the new unit unresponsive.
- Quick Fix: Bench flash spare unit offline to match existing stack master firmware build before stacking cable installation into live DCS network.
Commercial Availability & Pricing Note
Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.
