Control Network Newsletter
Understanding 10BASE-T1L
10BASE-T1L (T1L) is a physical layer specification for Ethernet introduced in IEEE 802.3cg that supports 10 Mbps, full duplex communication over single twisted pair cabling for distances up to 1 km. Single-Pair Ethernet (SPE) enables data and power transmission over a single twisted pair, reducing cabling complexity; while the extended reach makes T1L ideal for retrofits and long run applications where traditional Ethernet falls short.
BACnet/IP is the preferred protocol for interoperable building automation. However, conventional Ethernet cabling is typically limited to 100 meters, often requiring switches, media converters, or gateways to reach controllers, sensors, and actuators spread across large facilities.
T1L addresses this limitation because T1L is Ethernet, and BACnet/IP is an Ethernet based protocol. This means that protocol translation or gateways are not required—BACnet/IP runs directly over T1L just as it would over Cat5/6. T1L also enables seamless integration with IT networks, without needing a secondary fieldbus layer.
T1L simply replaces the cable type, using one pair instead of four, while extending Ethernet distances up to 1 km. For consulting engineers and systems integrators, this eliminates costly architectural workarounds and preserves BACnet/IP's simplicity across the entire control network.
Many existing buildings contain long runs of two-wire cabling originally used for MS/TP, Modbus, LON, or other legacy fieldbuses. T1L allows those same wires to be repurposed for full IP communications, reducing disruption and avoiding the expense of installing new Cat5/6 in occupied spaces. Building owners benefit from lower installation costs, and faster upgrades that require less downtime.
In many cases, a simple media adapter or T1L enabled controller is all that's needed to bring BACnet/IP to areas previously limited to non IP technologies.
A Contemporary Controls EIMK-T1L Media Converter connects a JACE to two BACnet unitary controllers over distances of up to 1 km.
T1L also supports Power over Data Line (PoDL) that allows power delivery alongside data transmission. This makes it possible to power smart sensors, room controllers, and small edge devices without the need for separate power supplies. For BACnet devices that rely on distributed sensors or space level controllers, this can significantly simplify deployment.
In summary, T1L brings Ethernet (and therefore BACnet/IP) to the edge of the building. It enables long distance IP-based communication, the ability to reuse existing wiring, and optional power delivery to minimize cost while improving network scalability.