How did they decide on those numbers?

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Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=57636
Printed Date: May 09, 2025 at 12:01 AM

Topic: How did they decide on those numbers?

Posted By: 704acc
Subject: How did they decide on those numbers?
Date Posted: June 13, 2005 at 10:54 PM

I have always wondered how they came up with the numbering system for the contacts of a 12 volt relay. Anyone know?

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Ray Kane

Replies:

Posted By: ff-mike
Date Posted: June 14, 2005 at 9:28 AM

Those numbers are loosely based on DIN, the German standardization body- the same people who defined the sizes of car stereos

Variations from DIN to what we see

Our#     Definition     DIN#
30       Common        87
85       relay coil(-)     85
86       relay coil(+)    86
87       n/o contact     87b
87a      n/c contact    87a

For more information, see Answers.com

Posted By: 704acc
Date Posted: June 14, 2005 at 10:15 PM

Thanks for the info. Any logic to why they picked such random numbers? For instance, does 29, 84, 88 etc. have any meaning in the "German standardization body"

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Ray Kane

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