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Single Pair Ethernet (SPE) is a next-generation communication technology that enables Ethernet connectivity over a single twisted pair of wires. It replaces bulky, heavy cabling systems while ensuring robust and stable networking across industries.

The IEEE 802.3cg standard defines two complementary SPE specifications: 10BASE-T1S and 10BASE-T1L. Each has distinct physical capabilities and target applications, designed to serve different yet complementary domains.

🔠 A Name With Meaning: Short vs. Long

The difference is in the name:

• "S" in 10BASE-T1S stands for Short-Reach
• "L" in 10BASE-T1L stands for Long-Reach

These labels reflect the optimized transmission range and deployment intent of each technology.
(e.g., 10BASE-T1S is ideal for short-range in-vehicle Ethernet, while 10BASE-T1L targets long-range industrial Ethernet communication)

🔍 10BASE-T1S: Optimized for Short Range and Multi-Drop Networks

10BASE-T1S enables connectivity across distances up to 25 meters. It supports multi-drop topologies, making it ideal for environments with numerous tightly packed nodes like vehicle networks or compact industrial devices.

Key Features

Speed: 10 Mbps

• Max Distance: 25 meters
• Duplex Mode: Half- or Full-Duplex
• Topology: Multi-drop or Point-to-Point
• Collision Avoidance: Uses PLCA (Physical Layer Collision Avoidance)

Applications

• Automotive sensor and actuator networks
• Internal device networks in machinery
• Localized robotics and control loops

Replaces Traditional Technologies

• LIN (Local Interconnect Network): Low-speed automotive network protocol typically used for body electronics.
• CAN (Controller Area Network): Widely used for in-vehicle networking and industrial automation.
• Short-distance RS-485: Serial communication often used in legacy automation systems for short-range, multi-drop setups.
• FlexRay: A time-deterministic communication protocol used in high-end automotive applications, which 10BASE-T1S can consolidate under Ethernet.

📅 Enhancing In-Vehicle Networks:

10BASE-T1S was designed for In-Vehicle Networking (IVN) systems. Modern cars integrate hundreds of sensors, actuators, lights, and switches, often managed by CAN, LIN, and other protocols. 10BASE-T1S aims to consolidate and streamline these systems.

• Short Range, High Density: Perfect for sub-15m environments within vehicles.
• Multi-Drop Efficiency: Enables multiple nodes on a single cable using PLCA.
• Lightweight Cabling: UTP cabling reduces harness size and vehicle weight.
• Robust EMI/EMC: Built for noisy automotive environments.

🔹 Key Insight: 10BASE-T1S brings standard Ethernet and multi-drop topology together to replace short-range fieldbus networks with a unified infrastructure.

🌐 10BASE-T1L: Long-Distance Ethernet for Industrial and Building Automation

10BASE-T1L delivers Ethernet communication over distances up to 1,000 meters. It enables seamless connectivity across sprawling industrial sites and building systems, replacing traditional analog or serial protocols.

Key Features

Speed: 10 Mbps

• Max Distance: 1,000 meters
• Duplex Mode: Full-Duplex
• Topology: Point-to-Point
• Power Delivery: PoDL (Power over Data Line) supported
• Encoding: PAM3

Applications

• Long-distance industrial automation
• Building automation systems (BAS, HVAC)
• Power-efficient remote sensor networks

Replaces Traditional Technologies

• RS-485, RS-422: Common serial standards used for robust industrial communication over moderate distances.
• CAN, CANopen: Legacy bus systems used in machinery and automation.
• Modbus RTU, Profibus DP: Widely adopted fieldbus systems used in process control and factory environments.
• HART, 4–20mA analog loops: Analog-based protocols used for simple sensor communications.
• FOUNDATION Fieldbus, PROFIBUS PA: Process automation networks that can be modernized with SPE while reusing existing cabling infrastructure.

📅 Transforming Industrial Ethernet:

10BASE-T1L shines in factory and building automation environments, where sensors, controllers, and power systems are spread across wide areas.

• Up to 1km Distance: Covers large-scale deployments effortlessly.
• PoDL Support: Delivers power and data through a single wire.
• Legacy Cabling Reuse: Works with existing fieldbus wiring (e.g., PROFIBUS PA).
• IT/OT Integration: Enables seamless communication from sensor to cloud.

🔹 Key Insight: 10BASE-T1L converges legacy serial/analog systems under the Ethernet umbrella for IIoT and smart factory modernization.

🖼️ Network Topologies in SPE: Multi-Drop vs Point-to-Point

To better illustrate the structural differences between 10BASE-T1S and T1L, the following diagram compares multi-drop and point-to-point network topologies.

In multi-drop configurations like 10BASE-T1S, multiple devices share a single cable segment, while 10BASE-T1L uses dedicated point-to-point links for each connection, suitable for longer distances and higher isolation.

🔎 Quick Comparison: T1S vs T1L

🌟 Conclusion

SPE is not just about reducing wires — it's about simplifying networks and enabling Ethernet everywhere.

• 10BASE-T1S is ideal for high-density, short-range environments like vehicles and embedded machinery. It replaces legacy multi-drop fieldbus systems.
• 10BASE-T1L supports reliable, long-distance Ethernet communication across industrial and building environments. It modernizes decades-old analog and serial infrastructure.

By adopting SPE, industries move one step closer to realizing Ethernet to the Edge — bringing standard networking from sensors all the way to the cloud.