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RUGGED COMPUTING · CONNECTORS

What Is M12 Coding?

M12 coding is the shape of the key inside an M12 connector that stops incompatible plugs and sockets being mated. Each coding is reserved for a job: A for sensors, DC power and general signals, B for PROFIBUS, D and X for Ethernet, and L, S, K and T for power. A plug only fits a socket with the same coding.

01

The Short Answer

Every M12 connector has the same 12 mm thread, so without coding a Gigabit Ethernet cable could be screwed onto a power socket. Coding adds a key and a pin layout unique to each use, so the connector physically refuses the wrong partner.

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    A-coded Sensors, actuators, DC power and general signals; 3 to 12 pins.
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    B-coded PROFIBUS fieldbus; usually 5 pins.
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    D-coded 4-pin 10/100 Mbps Ethernet, used for PROFINET and EtherNet/IP.
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    X-coded 8-pin Gigabit and 10 Gigabit Ethernet.
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    L, S, K and T-coded Power: L and T for DC, S and K for AC.
02

Each Coding in Detail

Read more about A-coded, B-coded, D-coded, X-coded and L-coded connectors, and the M12 power codings.

03

Coding on Industrial Computers

On a rugged or waterproof computer, the Ethernet ports are usually X-coded for Gigabit or D-coded for 100 Mbps, while serial, USB and DC power use A-coded connectors with different pin counts. Our guide to M12 connectors has the full coding table and pinouts.