Relay Terminal Standard Numbers

Posted on May 16, 2013 by Brian Gallimore

I finally did a little research to see if there was any meaning behind the numbers I often see on relays.  Of course there is!  It is European standard EN 50005.

  • NO: 3 and 4
  • NC: 1 and 2
  • Form C: 1 = common, 2 = NC, 4 = NO
25975_1000_int_04
relay-terminal-marking
siemens-2no-2nc

[Show slideshow]
This entry was posted in Industrial Automation and tagged , , , , . Bookmark the permalink.

One Response to Relay Terminal Standard Numbers

  1. Tony says:
    May 16, 2013 at 10:23 pm

    You’re just figuring this out?! Form A -NO, Form-B NC, Form C-both. As far as I remember I was born with this knowledge.

    Reply

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.