M12 Connector Codes Deciphered

A-coded M12 5 pin connector male/female pinout

Color coding for an A-code M12 5 pin connector.

The keying and pinout patterns are different for every M12 connector code and pin number. With sufficient familiarity a user should be able to identify a given M12 connector by the keying to identify the code and the number of pins to determine the exact M12 connector style. Otherwise, a simple identification chart like that depicted in Figure 1 should be adequate. Some suppliers include the pin IDs on the M12 connector face, which can aid in troubleshooting and maintenance when a connector may need to be serviced or repaired.

Along with cable assemblies, there are also M12 adapters, field termination connectors, splitters, multi-channel splitters, and bulk-head connector types. Hence, color-coded pinouts are useful to ensure proper connections during installation/hook-up, troubleshooting, and maintenance.

Quick Guide to M12 Connector Codes & Pins

• A-code
  • 2, 3, 4, 5, 6, 8, 12, and 17 pin configurations (4 and 5 pin are most common)
  • Used for sensors, actuators, low power, and low-speed data transmission
• Code
  • 4 and 5 pin configurations (5 pin is most common)
  • Used for fieldbus applications such as Profibus and Interbus
• Code
  • 2, 4, 5, and 6 pin configurations
  • Used for sensors and AC supply power
• D-code
  • 4 pin configuration only
  • Used for 100Mbps maximum data transmission for industrial Ethernet, Profinet, Ethernet/IP, EtherCat machine vision, and other applications, most commonly up to Category 5e standards
  • Capable of providing power via PoE (Power over Ethernet)
• X-code
  • 8 pin configuration only
  • Used for 10Gbps and high-speed data transmission applications, such as industrial Ethernet and machine vision, most commonly up to Category 6a or 7 standards
  • Capable of providing power via PoE (Power over Ethernet)
• Y-code
  • 6 and 8 pin configurations
  • Hybrid connector style
  • Used for both AC/DC power and data transmission in the same connector
  • Designed for applications where this hybrid configuration can make the interconnect solution more compact
• S-code
  • 2, 2+PE, and 3+PE configurations (4 pin, including the PE pin, is most common)
  • Used for power supply up to 630V and 12A or 16A per contact
  • Designed for AC power to motor operated switches, motors, frequency-converters, and other industrial equipment
• T-code
  • 2, 2+PE, and 3+PE configurations (4 pin, including the PE pin, is most common)
  • Rated to 63V and 12A or 16A per contact
  • Designed for DC power connections for small DC motors and fieldbus power
• K-code
  • 2, 2+PE, 3+PE, and 4+PE configurations (5 pin, including the PE pin, is most common)
  • Used for power supply to 800V and 16A per contact up to 10kW
  • Used for high power AC applications
• L-code
  • 2, 2+PE, 3, 3+PE, 4, 4+PE configurations (5 pin, including the PE pin, is most common)
  • Used for voltage up to 63V and 12A or 16A per contact
  • Designed for DC power connections for PROFINET and PROFIBUS devices
• M-code
  • 2, 2+PE, 3+PE, 4+PE, and 5+PE configurations
  • Rated to 630V and 8A per contact
  • Designed for 3-phase AC power connections

*PE typically refers to “Protective Earth”, this is a connection to ground that is used for safety purposes to protect users and equipment from electrical discharge in case of a fault. The PE pin is generally connected to the ground pin on an electrical supply plug or other connector ground. It is important to note that a ground pin in a connector may be a PE, but is not necessarily so, but every PE should only be used as a ground pin.

A-Code

A-code M12 connectors are also known as Micro-DC connectors and was one of the first styles of M12 connectors introduced. This style is widely used in factory automation applications, including sensors, actuators, control signals, and 1 Gbps data transmission. This connector can be used to power low-power DC motors and motor-operated switches. The data transmission on this connector is adequate for some machine vision applications, security, and Ethernet to 1 Gbps. The utility of this code is why A-code M12 connectors can be found in a wide range of industrial and enterprise applications from factory automation/control, transportation, agriculture, renewable energy, and telecommunications.

B-Code

B-code M12 connectors are specifically designed for use with fieldbus connections, including PROFIBUS and Interbus. Unlike other M12 connectors, the B-code is designed with a reversed single keyway. This allows for 2 distinct M12 connections to be mounted on the same panel without the risk of accidentally interconnecting the two systems. This is useful for installations that have different voltage/current configurations.

C-Code

C-code M12 connectors are sometimes also called Micro-AC and are typically only used for AC power applications. This could be bringing AC power to actuators, sensors, and other AC devices, such as factory automation equipment. These M12 connectors all have extended grounding pins and double keyways to ensure that improper insertion isn’t possible

D-Code

D-code M12 connectors are almost exclusively used for industrial Ethernet applications but may also be used for f ieldbus applications such as Profinet/Interbus, EtherCat, PoE (Power over Ethernet) or Ethernet/IP use cases. This code enables data transfer rates to 100 Mbps. The 4-wire setup of this connector accommodates 2-pairs of Cat 5e twisted pair cables. To allow for all 4 pairs of Cat 5e twisted-pair cables to be connected in single housing, 8-pin/wire A-code can be used.

X-Code

X-code is a more recent addition to the M12 connector styles. This code is now commonly used for high-speed industrial Ethernet applications and can transfer to 10 Gbps of data. This high rate of data transmission is possible with X-code connectors as the pairs of Ethernet wires are galvanically isolated using a metal structure within the connector housing. As many systems are moving to higher data rate Ethernet and transfer speeds, it is likely that X-code M12 will eventually replace A-code and D-code M12. X-code M12 connections can accommodate Cat 6A and Cat 7 connections and has 8 dedicated pins for full Ethernet 4-twisted pair connections. X-code is also capable of providing power via PoE (Power over Ethernet) to supported devices.

Y-Code

Y-code M12 connectors are a type of hybrid connector that includes 4 pins for data connections and 2 or 4 pins for power connections. This code has the same capability as D-code for data transmission but can also include 2 or 4 power pins that function similarly to A-code for a highly compact interconnect solution. Y-code connectors can be used for fieldbus applications and EtherCAT. The Y-code designation comes from the “Y” shaped face of the connector that is intentionally split to separate the data and power pins. This code is capable of up to 50 V AC/DC and 6A on the power pins or 0.5 A on the signal pins.

S-Code

S-code are among the newer M12 connector codes and will likely eventually replace C-code M12 parts. This code is designed for AC power applications to 630 VAC and 16A in either 1-phase, 2-phase, or 3-phase versions. The 3-phrase S-code connector is capable of 7.5 kW of AC power transmission, which makes it ideal for low-power AC motors, motor-controlled switches, and frequency converters.

Male/Female pinouts for S, T, K, L, and M code M12 connectors

T-Code

T-code M12 connectors are similar to S-code but are designed for DC applications to 63VDC and 12A per contact. This code is often used for fieldbus or Ethernet applications and can carry up to 750W of DC power, to power low-power DC motors/drives. It is likely T-code M12 connectors will eventually replace A-code connectors for DC power applications.

L-Code

Like T-code connectors, L-code M12 connectors are designed for use to 63V, but to 16A. This is ideal for high current but low voltage DC applications, such as fieldbus and Ethernet I/O boxes. L-code can also be made with a 4 pin with additional PE contact, where T-code is only available to 3 pin with PE contact.

K-Code

K-code M12 connectors are similar to S-code connectors, but some with an additional 4 pin and PE contact configuration. This code is also capable of 800V AC transmission with 16A per contact for a total of 10kW of AC power transmission per connector. This code is ideal for high power AC connections for motors and drivers.

M-Code

M-code M12 connectors are designed for up to 3-phase AC power transmission to 630V and 8A per contact. This code includes a PE for each pinout style except for a 2 pin style which does not include a PE contact.

P-Code

P-code M12 connectors are designed for up to 4 pin positions with a PE. These connectors are designed for data and can accommodate 2 twisted pair Ethernet connections at maximum pin positions. Though this connector type can be used for various functions it is generally used for EtherCAT applications.

Recommendations

• Check voltage/current/wiring requirements: For example, if you're supplying power-heavy field devices, use a connector rated accordingly (C- or L-coded) rather than a signal-rated A-code.
• Evaluate your application’s needs: Determine whether you need signal, fieldbus, Data-Ethernet, or power connectivity and choose the correct M12 coding accordingly (e.g., A for signals, D for Ethernet, C/L for power).
• Use proper keying and compatibility checks: Because connectors with different coding are not physically compatible, proper keying avoids accidental mismating.
• Consider environmental/industrial factors: Choose connectors with the required industrial IP rating (e.g., IP67) and durable construction suited for vibration, temperature, and humidity.
• Future-proof your system: If high-speed data or power redistribution might be required later, consider moving to connectors that offer higher ratings or codes designed for expansion (e.g., X-code for high-speed data).
• Document and label connectors clearly: Especially in complex automation systems, clear labeling of connector codes, functions, and wiring avoids maintenance errors and ensures correct replacement parts.
• Perform installation inspections and testing: Check that the connector mating is correct, shields/grounding are properly connected, and that the code selected matches the application.
• Train maintenance / installation staff: Ensure personnel understand the meaning of each M12 code, the risk of mismatching codes, and the style of connectors (male/female, thread size, etc.).

Conclusion

M12 interconnect is a highly versatile interconnect that is now widely used for factory automation and many other industrial applications. As the interconnect needs of these applications evolve, M12 interconnect is also evolving to accommodate higher data rates and higher power handling capability for multi-phase AC and DC applications.