Product Overview
The Foxboro A4H124-24FX P0973JN is a fully managed industrial fiber Ethernet switch engineered for high-reliability control networks inside the Foxboro I/A Series distributed control system environment and adjacent plant-floor automation infrastructure. Manufactured under the Enterasys SecureStack A4 platform and supplied to Foxboro/Invensys as a DCS-network-grade component, the Foxboro A4H124-24FX P0973JN delivers 24 dedicated 100Base-FX fiber-optic ports with MT-RJ connectors, supplemented by two mini-GBIC SFP bays and two 10/100/1000 RJ45 ports that function as either uplinks or closed-loop stacking interconnects. This port mix makes the unit particularly well suited to applications where long-distance, electrically isolated, and noise-immune communication between field cabinets, operator stations, and control processors is mandatory.
Architecturally, the Foxboro A4H124-24FX P0973JN operates as a non-blocking Layer 2 switching engine with a switching capacity of 12.8 Gbps and throughput of 9.5 Mpps, backed by an industry-standard MAC address table of 16,000 entries and support for up to 4,094 VLAN identifiers. Eight hardware-based priority queues per port, combined with strict and weighted round-robin scheduling, ensure that time-critical DCS traffic, alarm traffic, and supervisory data receive prioritized bandwidth ahead of bulk file or diagnostic transfers. Layer 2 resilience is provided through IEEE 802.1D, 802.1w Rapid Spanning Tree, and 802.1s Multiple Spanning Tree, while up to eight A4 units can be stacked into a single virtual switch of up to 102.4 Gbps aggregate capacity managed through one IP address.
For system integrators, OEM panel builders, and reliability teams maintaining mature Foxboro I/A installations, the Foxboro A4H124-24FX P0973JN remains a strategic network spare — one that bridges the gap between legacy 100Base-FX fiber infrastructure and modern gigabit uplink backbones without a full network rip-and-replace.
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | A4H124-24FX P0973JN |
| Manufacturer | Foxboro (Invensys / Schneider Electric) |
| Product Type | Managed Fiber Fast Ethernet Switch |
| Platform Family | Enterasys SecureStack A4 Series |
| Fiber Ports | 24 × 100Base-FX, MT-RJ connectors |
| Uplink / Stacking Ports | 2 × 10/100/1000 RJ45 + 2 × mini-GBIC (SFP) bays |
| Console Port | 1 × DB9 serial |
| Switching Capacity | 12.8 Gbps |
| Throughput | 9.5 Mpps (76.2 Mpps in 8-unit stack) |
| MAC Address Table | 16,000 entries |
| VLAN Support | Up to 4,094 VLAN IDs (IEEE 802.1Q) |
| Priority Queues | 8 hardware queues per port, 8 priority levels |
| Spanning Tree Support | IEEE 802.1D, 802.1w RSTP, 802.1s MSTP |
| Link Aggregation | IEEE 802.3ad LAG, up to 4 ports per group |
| Dimensions (H × W × D) | 4.4 × 44 × 36.5 cm (1.73 × 17.32 × 14.37 in) |
| Net Weight | 4.85 kg (10.69 lb) |
| Input Voltage | 100–240 V AC, 50/60 Hz |
| Power Consumption | 66 W maximum |
| MTBF | 388,135 hours |
| Operating Temperature | 0 °C to +50 °C (32 °F to 122 °F) |
| Storage Temperature | –40 °C to +70 °C (–40 °F to 158 °F) |
| Operating Humidity | 5 % to 95 %, non-condensing |
Main Features and Advantages
Dedicated 24-port 100Base-FX fiber access: The defining strength of the Foxboro A4H124-24FX P0973JN is its full complement of 24 fiber-optic Fast Ethernet ports. In industrial control environments, fiber eliminates ground loops, resists electromagnetic interference from variable-frequency drives, switchgear, and large motors, and supports cable runs far beyond copper’s 100-meter limit. The MT-RJ connector form factor matches the vast installed base of legacy Foxboro I/A fiber plant, so an existing network can be extended or a failed switch replaced without re-terminating hundreds of fiber links to a newer connector standard.
Gigabit uplink and stacking flexibility: Two 10/100/1000 RJ45 ports and two mini-GBIC SFP bays allow the to act simultaneously as a 100 Mbps access aggregation point and a gigabit uplink into the plant backbone. The same RJ45 ports double as stacking interconnects using closed-loop stacking (CLS), which permits up to eight A4 switches to form a single virtual switch with redundant management paths — so a switch-level failure inside the stack does not sever communication for the remaining members.
Deterministic Layer 2 switching with industrial-grade QoS: With eight hardware priority queues on every port, strict-priority and weighted round-robin scheduling, and a non-blocking 12.8 Gbps fabric, the guarantees that Modbus TCP, OPC, HART-over-Ethernet, alarm, and inter-controller synchronization traffic consistently outrank best-effort data. For control engineers who must defend loop update rates against background plant traffic, this queuing discipline is not cosmetic — it is the difference between a stable control loop and one that stutters under load.
Comprehensive security and management: The supports IEEE 802.1X port authentication, MAC-address authentication, web-based authentication, and role-based access control, allowing the plant network team to enforce per-port, per-device admission into the control VLAN. Management is available through CLI, web interface, SNMP, and secure in-band channels, enabling integration into existing network-monitoring systems.
Investment protection through stacking and modularity: Because the participates in the SecureStack A4 stacking architecture, capacity can be added incrementally by inserting additional A4 units — including copper-port variants — into the same stack rather than redesigning the network topology. This staged-growth model is particularly valuable in capital-constrained plant environments where a phased upgrade is preferable to a single large outage.
Proven industrial reliability: With an MTBF of 388,135 hours and a heritage of deployment inside Foxboro I/A Series DCS installations worldwide, the carries an operational pedigree that generic commercial switches cannot claim, making it a low-risk choice for mission-critical control network segments.