A-Code, B-Code, D-Code: Understand M12 Coding Differences & Applications in 1 Minute!

If you work with industrial sensors, automation, or IoT devices, you’ve probably come across M12 connectors. But do you know why their coding (A/B/D) matters? Let’s break it down simply:

1. What’s M12 Coding Anyway?

M12 connectors use coding (keyways) to prevent wrong connections—critical for avoiding equipment damage or signal failures in harsh industrial environments (think factories, robotics, or outdoor tech).

2. A-Code: The “Everyday” Choice

• Pinout: 4/5 pins (common for power + signal).

• Best For: Basic sensors (proximity, photoelectric), industrial Ethernet (PROFINET, Ethernet/IP) in non-safety-critical setups.

• Why pick it? Widely available, cost-effective for standard automation tasks.

3. B-Code: Safety First

• Pinout: 4/5 pins (but with reversed pin assignments vs. A-Code—no mix-ups!).

• Best For: Safety-related devices (emergency stops, safety sensors) or fieldbuses like PROFIBUS.

• Why pick it? The reversed pinout ensures you can’t accidentally plug a safety device into a non-safety port—compliant with industrial safety standards.

4. D-Code: Speed & Data Heavy

• Pinout: 4 pins (optimized for high-speed data).

• Best For: Fast Ethernet (100BASE-TX, 1000BASE-T) in demanding setups—robotic arms, high-speed vision systems, or IoT gateways.

• Why pick it? Minimizes crosstalk (signal interference) for reliable, high-bandwidth data transfer.

Quick Tip: Always match the coding to your device’s specs—A for standard, B for safety, D for speed!

Guangdong Corecon Precision Industry Co., Ltd. specializes in various industrial connector, push-pull self-locking connectors, new energy connectors, M series connectors , waterproof connectors, electric bicycle signal and power connector, and all kinds of wire harnesses. If you have any questions related to the connector industry, please contact us and we will provide you with free, one-stop professional solutions within 24 hours.