M125 pin connectorpinout

IEC metric screw sized connectors is a family of electrical connectors defined by IEC that are named according to their ISO metric screw thread, namely M5, M8 and M12.[1] The number gives their outer screw thread diameter in millimeters as with the identically named screws. However, the connectors are further classified by a so-called coding, denoted by one or more letters, which defines things like pin layout, shape of connecting surfaces and electrical properties.[2][3]

M124pinout

The many types are partly to prevent incorrect connection.[2] The larger connector sizes are the most varied, with designated connectors ranging from analog and digital signals to AC and DC power.[4]

M12connector wiring diagram

Major uses include factory automation and transportation.[2] Products can be designed for high weather and chemical resistance (high IP rating)[2] as well as mechanical durability.[1]

All variants permit one or more pins to be removed to create differently keyed connectors.[7] For example any pin in a 6-pin connector could be removed, to make six different, incompatible 5-pin connectors.