Foxboro P0973JN (A4H124-24FX) 24-Port 100BASE-FX Managed Fiber Ethernet Switch

Product Overview

The Foxboro P0973JN, listed in Enterasys (now Extreme Networks) product records as the A4H124-24FX, is a high-density, Layer 2 managed fiber Ethernet switch purpose-built for the fiber-optic access and aggregation layer of Foxboro I/A Series distributed control system (DCS) networks. In Foxboro asset catalogs, P0973JN is the assigned order/asset number for a single-unit A4H124-24FX chassis with internal AC power supply; the P0973JP variant is the same chassis plus an external redundant power supply module. The switch carries pre-configured SecureStack A4 firmware and is qualified for deployment in Foxboro I/A Series and EcoStruxure Foxboro control architectures, where it provides deterministic, noise-immune optical transport between field control processors, I/O subsystems, operator and engineering workstations, and gateway devices.

Physically, the Foxboro P0973JN​ is a 19-inch, 1U rack-mount appliance. It is built around the Enterasys SecureStack A4 platform and offers 24 fixed 100BASE-FX fiber ports for field-side connections, two 1000BASE-X mini-GBIC (SFP) uplink slots for Gigabit fiber or copper expansion, and two dual-purpose 10/100/1000BASE-T RJ45 ports that serve as Gigabit uplinks or stacking/inter-switch links (ISL). With 12.8 Gbps of switching capacity, 9.5 Mpps forwarding throughput, a 16,000-entry MAC address table, support for up to 4096 IEEE 802.1Q VLANs, and jumbo frames up to 9216 bytes, the Foxboro P0973JN​ is engineered to handle control traffic, historical data, and alarm streams without creating bottlenecks at the edge of the control network.

Its core value lies in combining optical isolation with enterprise-class manageability. In electrically hostile process environments—motor control centers, variable-frequency drive rooms, high-voltage switchyards, and long-distance inter-cabinet links—the all-fiber access design eliminates ground loops and provides inherent immunity to electromagnetic interference (EMI). Full management through CLI, WebView, SNMP v1/v2c/v3, SSH, Telnet, and RMON, together with redundant power and stacking options, makes the unit suitable for both new control-network builds and long-service-life brownfield DCS installations.