M12 Coding Cheat Sheet

This is the print-friendly version of §8.1 in the M12 deep dive. Use it to get into the right neighborhood, then let the exact part's datasheet make the final call.

The keyway and insert geometry keep different codings from mating. Exact geometry comes from IEC 61076-2-101/-109/-111 and the manufacturer drawing. The standards make cross-vendor interoperability possible, not automatic: you still need to check code, pin count, gender, shielding, sealing, torque, and the full cable assembly.

The codings

Code	Pins	Primary use	Practical note
A	3/4/5/8	DC sensors, actuators, I/O, IO-Link, some CAN	4-pin A-coded is extremely common for basic industrial sensors. IO-Link = a point-to-point digital sensor/actuator protocol carried over the same unshielded 3–4 wires.
B	5	PROFIBUS and similar fieldbus	Less common in new systems; keyed differently from A
D	4	10/100BASE-TX industrial Ethernet	4-pin; commonly used for 10/100 Mbps; not rated for GbE/10G
X	8	Gigabit / 10G-class industrial Ethernet	8-pin, shielded; used for GbE/10G applications
L	4+FE	Higher-current DC power (e.g. PROFINET power)	4 power contacts + FE (functional earth) per DIN EN 61076-2-1111; vendor example rating 12 A/16 A at 63 V DC — distributed I/O power, higher current than A; verify exact rating by catalog
T	4	DC power (dedicated)	4 contacts per DIN EN 61076-2-1111; vendor example rating 12 A at 63 V DC — verify exact rating by catalog
S	4/5	AC power	Application-specific; verify by catalog
K	4+PE	AC power	4 power contacts + PE (protective earth); the 630 V AC class is an example configuration per IEC 61076-2-1112, not a universal M12 rating — verify exact current, voltage, and pinout by standard edition and catalog/application

Schematic face views of the four most common codings.

Which standard covers what

• IEC 61076-2-101 — many common A/B/D signal/data codings.³
• IEC 61076-2-109 — X- (and H-) coded high-speed data.⁴
• IEC 61076-2-111 — power codings such as S/T/K/L.⁵

The two mix-ups this sheet exists to prevent

• A-coded current: many A-coded M12 connectors are in the ~4 A class within common standard/catalog scopes,³ but the exact rating depends on the connector, cable assembly, wire gauge, loaded contacts, and temperature. Use L-, T-, or other power codings where the exact datasheet supports the load.
• D vs. X: D-coded is not obsolete — it is the common 10/100BASE-TX choice.³ X-coded is for GbE/10G-class Ethernet⁴ and is not a blanket default for every Ethernet use. Choose by data rate, then verify cable category, shielding, pinout, and assembly rating.

Record before you commit

• Coding and pin count, from the drawing (not the listing photo)
• Standard identifier and edition/date checked
• Manufacturer datasheet revision used for the design
• Exact current/voltage rating for the loaded configuration
• Gender, shielding, sealing (mated and unmated), and coupling torque per the exact datasheet

note

This is a working reference, not a standard. The datasheet, applicable standard, and customer/program requirements always win. Scenario walkthroughs: Industrial sensor · Rugged Ethernet.

Sources

Footnotes

1. binder, M12 L-coded and M12 T-coded product families (screw locking per DIN EN 61076-2-111) — "L-coded versions have 4+FE contacts" with a rated current of 12 A/16 A at 63 V DC; "T-coded versions have 4 contacts with a rated current of 12 A at 63 VDC." Vendor example configurations, not universal M12 ratings — verify the exact datasheet. L-coded: https://www.binder-usa.com/us-en/products/automation-technology-voltage-and-power-supply/m12-l — T-coded: https://www.binder-usa.com/us-en/products/automation-technology-voltage-and-power-supply/m12-t ↩ ↩²

2. binder, M12 K-coded product family — "K-coded connectors with screw locking according to DIN EN 61076-2-111 are designed for AC applications and have 4+PE contacts" (630 V class; vendor current ratings vary, e.g. 12 A — verify the datasheet). https://www.binder-usa.com/us-en/products/automation-technology-voltage-and-power-supply/m12-k ↩

3. IEC 61076-2-101, Connectors for electronic equipment — Product requirements — Part 2-101: Circular connectors — Detail specification for M12 connectors with screw-locking (A/B/D coding): 2- to 17-way; data transmission up to 100 MHz; signal and power up to 250 V and up to 4 A per contact. https://webstore.iec.ch/en/publication/77773 ↩ ↩² ↩³

4. IEC 61076-2-109, … Part 2-109: Circular connectors — Detail specification for connectors with M12 × 1 screw-locking, for data transmission frequencies up to 500 MHz — covers the X- and H-coded variants; X-coding supports Cat 6A / up to 10 Gbit/s at IP65/IP67. https://webstore.iec.ch/en/publication/4425 ↩ ↩²

5. IEC 61076-2-111:2025, Connectors for electrical and electronic equipment — Product requirements — Part 2-111: Circular connectors — Detail specification for power connectors with M12 screw-locking — per the current edition's abstract: 4- to 6-way connectors "with current ratings 8, 12 or 16 A per contact and voltage ratings of 50 V AC / 60 V or 630 V according to their coding." Treat these as edition- and configuration-specific scope figures, not universal M12 power ratings. https://webstore.iec.ch/en/publication/89862 ↩