MX Circular Connectors

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MX Circular Connectors include all circular connectors designated with M and a thread diameter in millimeters, e.g. M5, M8 and M12 connectors.

M8 and M12 connectors are circular connectors with a 8mm or 12mm mating thread (note the thread in question is the thread joining the two mating connectors together, not the other threads which may be present on the M12 connector, such as panel-mount variants which typically have a 16mm thread for mounting to the panel). They are used for a variety of purposes across a large number of industries. A large number of these connectors are rated IP67 and prevent the ingress of water and dust.

Smaller M5 connectors also exist, which include 2, 3 and 4pin configurations1.

M8/M12 connectors have different codings. Each coding is a particular pin arrangement and key which prevents the same diameter and pin connector being mated with connectors with different codings.

  • A: Sensors, DC power (deprecated use), 1Gbit Ethernet. This is a very common/popular encoding.
  • C: AC power (deprecated)
  • D: 100Mbit ethernet
  • K: AC power
  • L: PROFINET DC power
  • N:
  • S: AC power (replacement for C)
  • T: DC power (replacement for A DC power)
  • X: 10Gbit Ethernet

Common pin counts (larger pin counts are only available in the larger diameter connector):

  • 4 (M8, M12)
  • 5 (M12, sometimes M8)
  • 8 (M12)
  • 12 (M12)

Some of the panel mount M12 connectors have a M16 (16mm) panel mount thead, others have a PG9 (see thread.

Inline Connectors

They typically have a PG7 or PG9 thread. The PG9 thread seems to be more common/widely available. The inline connectors may have screw termination (terminal block style).


The M8/M12 connector family also come with splitters — Y and T shaped units which allow 3 cables to be connected together.

Field Installable Connectors

Some M8/M12 connectors are field installable. This is when the connection to the wire is done via terminal block style screw cages (or similar) on the backside of the connector. No crimping tool or soldering is required, hence they are able to be made on the fly in the “field”.


Phoenix Contact

Phoenix Contact make a number of circular connector product in the M5, M8 and M12 range under their PLUSCON brand name. A good brochure listing many of their M5 to M12 products can be found at Some of the offerings include Litz wires.


NorComp manufacture a range of M5, M8 and M12 circular connectors.


  1. NorComp. M5 Connector Series (product page). Retrieved 2022-06-10, from↩︎


Geoffrey Hunter

Dude making stuff.

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