Skip to main content
Contact Us
RUGGED COMPUTING · CONNECTORS

What Is an M12 D-Coded Connector?

An M12 D-coded connector is the 4-pin M12 coding for 10/100 Mbps Ethernet. It is used for PROFINET, EtherNet/IP and other industrial Ethernet networks, and for many rail and vehicle networks. Pins 1 and 3 carry the transmit pair and pins 2 and 4 the receive pair.

01

The Short Answer

D coding was the first M12 coding for Ethernet. Four pins carry the two twisted pairs that 100BASE-TX needs, which is enough for most sensors, drives and controllers, but not for Gigabit Ethernet.

  • //
    Pins 4, in two twisted pairs.
  • //
    Speed 10/100 Mbps (Fast Ethernet).
  • //
    Pinout Pin 1 TX+, pin 2 RX+, pin 3 TX-, pin 4 RX-.
  • //
    To RJ45 Maps to RJ45 pins 1, 3, 2 and 6.
  • //
    Networks PROFINET, EtherNet/IP, EtherCAT and rail networks.
02

D-Coded or X-Coded?

Choose D-coded where the network is 100 Mbps and the devices already use it. For Gigabit or faster links, including most modern computers and cameras, use X-coded M12 instead; the two do not mate. The M12 to RJ45 FAQ shows how to join either to a standard network. Our guide to M12 connectors compares every coding, and the M12 coding FAQ explains how coding works.