Eliminating Protocol Gateways in Discrete Manufacturing with Managed Single Pair Ethernet Switching

Many discrete manufacturing networks carry a gateway layer between the field level and the main Ethernet network. Each gateway translates protocols between the two layers and adds configuration, maintenance, and troubleshooting overhead. As device counts grow, that overhead grows with them.

This article explains how single-pair Ethernet can reduce or remove the need for protocol gateways by extending Ethernet connectivity directly to field-level devices. The implementation draws from the BEETLE SPE Lite Managed Switch and SPE connector accessories for the field-level connections.

The gateway problem in discrete manufacturing

These networks often use hybrid architectures built up over time. Field devices may communicate through protocols such as IO-Link or other legacy field-level links, while gateway devices convert that traffic into Ethernet for the plant network. Each additional gateway is also a potential fault point that becomes harder to isolate as the count grows.

SPE-capable switching can connect field devices directly to the Ethernet layer, allowing plants to reduce the gateway count incrementally without replacing the legacy installation in a single step.

How single-pair Ethernet enables field-level IP connectivity

Single-pair Ethernet extends standard Ethernet to field devices using a single twisted pair. Three specifications define the physical layer, power delivery, and connector interfaces that make that connection practical in discrete manufacturing environments.

IEEE 802.3cg adds 10BASE-T1L, a single-pair Ethernet physical layer that operates at 10 Mb/s over a single twisted pair and supports distances up to 1 km. That range is far beyond the 100 m limit of conventional twisted-pair Ethernet, making it well suited to longer industrial runs. In systems where both the field device and switching infrastructure support 10BASE-T1L natively, direct Ethernet connectivity can reduce or eliminate the need for a protocol gateway.

IEEE 802.3cg extends the IEEE 802.3bu Power over Data Lines (PoDL) specification, enabling DC power to be delivered to field devices over the same single twisted pair used for data. For devices with moderate power requirements, PoDL can eliminate the separate power cable that traditional fieldbus installations often require. This, in turn, reduces wiring labor and the number of cable entries at the device housing.

IEC 63171-6 defines SPE connector interfaces for field connections, including M8 hybrid connector housing options for IP65/67 environments. For higher-power applications requiring M12 form factors, IEC 63171-7 specifies SPE-M12 hybrid connectors. Both M8 and M12 are established sizes in existing fieldbus and sensor wiring.

Together, these specifications provide the means to connect sensors, actuators, and instruments directly to an IP network using a single cable, a standard connector, and an SPE-capable switch at the field edge.

BEETLE SPE Lite Managed Switch

The BEETLE SPE Lite Managed Switch from Lumberg Automation serves as the edge node that makes SPE networks operational in a discrete manufacturing context. The switch implements 10BASE-T1L and PoDL at the field edge, putting the 802.3cg and 802.3bu specifications into practice in a DIN rail-mounted form factor. Figure 1 shows the front panel arrangement with the eight M8 downlink ports and the RJ45 uplink ports.

Figure 1: BEETLE SPE Lite Managed Switch (BTL12-08T1-02TX-L) with eight M8 10BASE-T1L downlink ports and two RJ45 100BASE-TX uplink ports. (Image source: Belden)

Hardware configuration: The switch is DIN rail-mounted in an IP40-rated housing and operates on a 24 V DC supply. Eight M8 downlink ports connect directly to 10BASE-T1L-capable field devices. Two RJ45 uplink ports connect the SPE field segment to the existing 100BASE-TX Ethernet infrastructure at the panel level. The operating temperature range of -10°C to +60°C covers the ambient conditions typical of machine enclosures in discrete manufacturing environments.

Network segmentation and traffic management: Figure 2 illustrates a VLAN configuration that isolates field device traffic from management and supervisory traffic on the same physical switch, eliminating the need for a separate management network device at the field edge. Quality of service (QoS) prioritizes time-sensitive control traffic over lower-priority data flows.

Figure 2: VLAN configuration separating field device traffic from management traffic on the BEETLE SPE Lite Managed Switch. (Image source: Belden)

Security at the edge: Port security disables unused switch ports to prevent unauthorized physical connections. Figure 3 details how ACL rules applied at the switch port level control which traffic a field device can send and receive. This filtering adds no latency and requires no dedicated firewall in the network path.

Figure 3: Access control list rules controlling data flow between a field device and the network on the BEETLE SPE Lite Managed Switch. (Image source: Belden)

Management and integration: An embedded web server provides switch configuration without specialized software or a separate management workstation. Integration with existing SCADA and MES systems is supported through OPC UA, EtherNet/IP, and Modbus TCP.

SPE connector accessories for the field level

Connecting the BEETLE SPE Lite Managed Switch to field devices requires panel-mount connectors that implement the IEC 63171-6 and IEC 63171-7 interfaces. The selected connector must also match the IP rating, thread size, and mounting orientation of the installation. Lumberg Automation offers SPE wall mounting screws that cover the M8 and M12 connector sizes and both rear and front panel mounting configurations.

M8 SPE rear wall mounting screw: This screw-locking M8 connector is designed for rear panel mounting and accommodates panels with a 7 mm wall thickness. The nickel-plated housing achieves IP65 and IP67 ratings when mounted and locked in combination with a compatible Hirschmann or Lumberg Automation connector, and the connector carries a UL 2238 listing.

Figure 4 provides the GKMH1X7L connector profile and key specifications. For installations with thicker panel walls, the GKMH1X8L and GKMH1X9L variants provide the same interface at 8 mm and 9 mm panel thicknesses, respectively.

Figure 4: M8 SPE (GKMH1X7L) rear wall mounting screw for 7 mm panel thickness with screw-locking coupling and IP65/IP67 housing. (Image source: Belden)

M12 SPE rear wall mounting screw: This connector uses an M12 x 1 thread and a nickel-plated housing, and it supports both screw-locking and push-pull coupling to accommodate installations where field technicians must connect and disconnect under confined conditions. The connector achieves its IP rating when mounted and locked in combination with a compatible Hirschmann or Lumberg Automation connector. Figure 5 shows the GK2F6XZB M12 interface and coupling options.

Figure 5: M12 SPE (GK2F6XZB) rear wall mounting screw with screw-locking and push-pull coupling options. (Image source: Belden)

M12 SPE front wall mounting screw: The GK2H6XZB uses the same M12 x 1 thread and nickel-plated construction as the GK2F6XZB and supports both screw-locking and push-pull coupling. This variant is configured for front panel mounting, serving installations where rear panel access is not available during maintenance, including enclosed machine cabinets with fixed back panels.

The front-mount orientation makes the connector accessible from the front of the enclosure without requiring panel removal. The connector achieves its IP rating when mounted and locked in combination with a compatible Hirschmann or Lumberg Automation connector. Figure 6 depicts the front-mount profile.

Figure 6: M12 SPE (GK2H6XZB) front wall mounting screw configured for front panel access, with screw-locking and push-pull coupling options. (Image source: Belden)

Conclusion

Discrete manufacturing networks have accumulated a gateway layer that converts fieldbus signals to Ethernet at the panel level. Each gateway adds configuration overhead, maintenance burden, and a point of failure in the field device data path.

The BEETLE SPE Lite Managed Switch removes that layer at the field edge. Its eight 10BASE-T1L downlink ports connect field devices directly over distances up to 1 km, and PoDL delivers power over the same pair, eliminating the separate power cable. VLAN segmentation, port security, and MAC-based ACL filtering control traffic at the switch port level without a dedicated firewall. The mounting screws complete the physical-layer connection for M8 and M12 field device installations.