Figure (above): Contemporary Controls EIMK-T1L Media Converter connects a PLC to an HMI and drive over distances of up to 1 km.

Ethernet has long been the backbone of industrial and building automation networks, but distance has traditionally been a limitation. Conventional copper-based Ethernet is typically limited to 100 meters, often requiring switches, fiber links, media converters, or gateways to reach controllers, sensors, and actuators distributed across large facilities.

A newer standard, 10BASE T1L (T1L), enables long distance, IP based networking over a single twisted pair of copper wires. Unlike standard Ethernet, which requires two or four wire pairs, T1L extends Ethernet’s reach while preserving familiar networking tools and protocols.

Published by IEEE in 2019 and incorporated into the IEEE 802.3 2022 standard, T1L defines a physical layer that supports 10 Mbps, full-duplex Ethernet communication over distances up to 1 km using Single-Pair Ethernet (SPE).

T1L enables both data and power transmission over a single twisted pair, simplifying cabling. Its extended reach makes T1L ideal for retrofit and long-run applications.

Older Ethernet standards, such as 10BASE-T, 100BASE-TX and 1000BASE-T, require specific types of cable, CAT-5, CAT-5e, CAT-6, etc. 10BASE-T1L offers greater flexibility, as it can operate over a wide range of single-pair cables. However, the distance between devices can be affected by cables with higher insertion loss. It may be possible to reuse existing cables, such as those used for RS-485 communications.

The IEEE 802.3 standard offers a variety of copper varieties, interoperability and fiber versions, but no auto-negotiation.

Key Features of T1L:

• 10 Mbps full duplex Ethernet
• Distances up to 1 km over copper
• Communication over a single twisted pair
• Native IP communication
• Polarity insensitive wiring
• More cable options than 10BASE-T, 100BASE-TX or 1000BASE-T
• Support for industrial environments, including intrinsically safe installations

10BASE-T1L vs Standard Ethernet

Contemporary Controls EIMK T1L media converter

Unlike standard Ethernet, which requires two or four wire pairs, T1L simplifies cabling while extending reach by a factor of ten. Higher speed Ethernet standards, such as 100BASE TX, 1000BASE T, or 10GBASE-T, offer higher bandwidth but are limited to 100 meters. At 10 Mbps, T1L delivers speeds roughly 100 times faster than typical a RS-485 network, while operating over distances comparable to legacy fieldbus systems.

Auto-Negotiation

Standard Ethernet devices use auto-negotiation to automatically determine the optimal mutually supported communication speed and duplex mode (half or full). This allows 10BASE-T devices to communicate with 100BASE-TX, 1000BASE-T, 10GBASE-T, etc.

In contrast, T1L operates at a fixed 10 Mbps full duplex and does not perform speed or duplex negotiation with the 100BASE-TX, 1000BASE-T, 10GBASE-T devices.

T1L devices support operation at 1.0 Vpp or 2.4 Vpp to accommodate varying link lengths and power requirements. These voltage levels can be configured or negotiated between T1L devices.

• 1.0 Vpp is used for intrinsically safe environments, such as oil and gas.
• 2.4 Vpp enables maximum distance (up to 1 km), depending on cable quality.

The lower voltage can reduce maximum distance on some cables compared to 2.4 Vpp, but higher quality cabling often maintains full reach.
Note: In some implementations, extended distance can be achieved by configuring both T1L devices to operate at 2.4 Vpp.

Connecting Standard Ethernet to 10BASE-T1L

Standard Ethernet and T1L operate on different physical layers, so they cannot connect directly. A media converter can be used to interconnect these two networks.

A 10BASE-T to 10BASE-T1L media converter allows standard Ethernet devices to communicate over long single-pair links.

Unlike Ethernet switches, which store and forward frames (entire messages), media converters typically forward data bit-by-bit at the physical layer, reducing the delay through the interconnecting device.

The Contemporary Controls EIMK T1L media converter complies with IEEE 802.3-2022 and enables full duplex, 10 Mbps, communication between 10BASE-T Ethernet and 10BASE-T1L networks. Its 10BASE-T port can be connected to any standard copper Ethernet device (100BASE-TX, 1000BASE-T, etc.).

Key Features

• The built-in microcontroller provides protection against brownouts and voltage fluctuations in the field.
• Four external DIP switches for configuring advanced features:
• Link Passthrough: Propagates link status between ports for fault detection and provides support for BMS devices in RSTP ring topologies.
• T1L Line Voltage: Selects 1.0 Vpp or 2.4 Vpp operation.
• Auto-negotiation: Configures T1L link behavior.
• Extended Mode: Enables longer distances when used in matched pairs.

Cable Reuse and IP Compatibility

T1L supports both new and retrofit applications because it can operate over both legacy wiring and standard Ethernet cables, such as Cat5e or Cat6, combining the advantages of Ethernet with the flexibility and extended reach of fieldbus and serial networks.

Many factories contain existing two-wire cabling originally used for MS/TP, Modbus, LON, or other legacy fieldbuses. In most cases, this wiring can be reused for T1L, allowing upgrades from legacy serial networks to IP-based networks without replacing existing infrastructure. Building and factory owners benefit from lower installation costs and faster upgrades that require less downtime.

Though existing cabling can often be reused, whether full distance is achievable depends on factors such as cable type and quality, insertion loss, operating voltage, and environmental conditions.

While traditional Ethernet requires additional infrastructure, such as switches or gateways to exceed 100 meters, T1L eliminates this limitation.

Because T1L is part of the Ethernet standard, it carries IP traffic natively. Protocol translation or gateways are not required because IP runs directly over T1L just as it would over standard Ethernet networks, such as 10BASE-T, 100BASE-TX, 1000BASE-T, etc. Controllers, sensors, and actuators that previously used non-IP fieldbuses can now be upgraded to Ethernet-based versions to participate fully in IP networks over long distances. T1L also enables seamless integration with IT networks, without the need for a secondary fieldbus layer, making cloud connectivity for data analytics and predictive maintenance easier.

T1L effectively replaces the cabling layer, using one pair instead of four, while preserving Ethernet functionality, retaining IP compatibility, simplifying architecture, and reducing installation costs.

Summary

In summary, T1L extends Ethernet to the edge of building and industrial networks by enabling long-distance IP-based communication over a single pair of wires. It allows the reuse of existing wiring while extending network reach and improving network scalability. When used with a media converter, T1L provides seamless connectivity between standard Ethernet and T1L networks, enabling migration from legacy systems to modern IP infrastructure.

T1L provides support for:

• Up to 1,000 m reach (vs. 100 m for standard Ethernet)
• A variety of cables, including reuse of existing cabling
• Simplified wiring (single-pair vs. multi-pair)
• Native IP communication and routing
• Modbus TCP and other Ethernet protocols, including IP routing and security
• RSTP for network redundancy

Harpartap Parma, Director of Product Management, Contemporary Controls