Industrial Automation

Need an M12 Connector? Don’t Forget to Ask about Coding!

Jeremy Friedmar

When someone talks about needing M12 connectors as part of an upcoming project, there’s one follow-up question you should always ask: What kind of M12 connector? The decision goes beyond simply selecting an M12 connector.


Think about asking someone to go to the store to purchase a light bulb. It seems easy enough on the surface, but they’ll realize there are several options to choose from based on preferences and applications. The same holds true for M12 connectors.


At quick glance, it’s difficult to tell one M12 connector from another. Instead, the vital differences can be found inside the connector in terms of how it’s keyed in the connector insert and how the pins are configured which prevent or allow mating. These configurations are called the connector’s “coding”; codings are necessary to be able to differentiate and identify the various M12 connectors.


As workers in the field or on the plant floor disconnect, reconnect and install new connectors quickly, codings also ensure that an M12 connector is never inserted into the wrong circuit or used in the wrong application. (This is one of the reasons electrical outlet plugs vary between Europe and the United States, too: They feature different shapes to prevent mis-mating.) When you try to plug an M12 connector into the wrong receptacle, it won’t fit.


A wide range of codings makes M12 connectors applicable within many different markets and applications. They can often be found in agriculture, alternative energy, communications, factory automation, food and beverage, measurement and control, robotics and transportation.


Here’s a quick and straightforward overview of what the most common M12 codings mean and where they can be used …


The 5 Most Common M12 Connector Codings

M12 A-coded connectors are widely used and have been around for decades. They’re also the most versatile in terms of the types of connections they support, as well as the number of pins housed in the connector (between three and 12 or even more). They support direct current (DC) connections and are used to connect sensors and actuators, as well as Ethernet connections up to Category 5e (four-pair connections).


M12 B-coded connectors are for network or non-Ethernet fieldbus connections (the most common is PROFIBUS). They can be used for sensor connections as well. Over time, we may see fewer of these connectors in use as PROFIBUS and similar fieldbus protocols are replaced with Ethernet.


M12 C-coded connectors are used for alternating current (AC) applications, including motor connections. In the future, we predict that some of the applications currently calling for M12 C-code connectors may transition to K-coded and S-coded connections (see below to learn more about these codings).


M12 D-coded connectors are used primarily for industrial Ethernet connections, such as PROFINET and EtherNet/IP. They provide a form factor that supports two-pair connections. Unlike M12 X-coded connectors, D-code doesn’t support Gigabit Ethernet; it only supports Fast Ethernet (100 Mb/s).


Lastly, M12 X-coded connectors are a more recent development designed specifically to support Gigabit Ethernet. In addition to preventing mis-mating, these connectors are designed with walls between each group of two pins (four groups of two pins overall). The walls prevent crosstalk and interference to achieve excellent Category 6 or 6A performance (up to 10 Gb/s).


Additional M12 Codings You Need to Know for Power Connections

This brings us to the next group of M12 connectors, which support higher voltage and current ratings over M12 connections. In these connectors, the pins are spaced in a way that provides proper electrical capabilities and prevents mis-mating:


  • M12 K-coded connectors have five pins, are intended for AC connections (AC motors, motor-operated switches, PSUs, etc.) and are rated for 630 volts.
  • M12 S-coded connectors have four pins, are also intended for AC connections and are rated for 630 volts.
  • M12 L-coded connectors have either four or five pins, are intended for DC connections (DC motors and drives, LED fixtures, I/O modules, etc.) and are rated for 63 volts.
  • M12 T-coded connectors have four pins plus a functional earth pin, are also intended for DC connections and are rated for 63 volts.


And, finally, we have the M12 Y-coded connector. This hybrid connector supports power and data connections over the same connector; inside, a wall separates the power and data pins. This can save valuable space and reduce installation time and material in applications that call for both.


The next time someone mentions an M12 connector, make sure you ask: What kind of M12 connector do you need? Knowing the answer will save time and reduce frustration when you’re ready to make your selection.