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Basic Switch: NO, NC and COM Contact Terminal

What is the relationship between the contact terminals NO, NC, and COM and the contact structures of contact points a, b, and c?


The symbols for contact terminals are NO terminal, NC terminal, and COM terminal. Each sign represents a single terminal: Normally Open, Normally Closed, and Common terminals, respectively.


Contact point a, contact point b, and contact point c, on the other hand, depict contact structures. Make contact point, Break contact point, and Transfer contact point are all terms that refer to the combination of two or more contact terminals. Contact point 1a refers to a contact structure with a single combination of contact point a, while contact point 2a refers to a contact structure with two combinations of contact point a.


In terms of the relationship between contact terminals and contact structures, contact point an is made up of two NO terminals, contact point b of two NC terminals, and contact point c of a single NO, NC, and COM terminal. As a result, contact point 1c can be used as contact point 1a or 1b, but not as contact point 1a1b. This is due to the fact that contact point 1c contains a COM terminal on one side, making it impossible to separate.


The contact points a and b are sometimes referred to as NO and NC contact points, however the JIS C 0301 Graphical Symbols for Diagrams refers to them as contact point a and contact point b, respectively.


Refer to the diagrams below for a description of the JIS C0301 Series 1 contact point symbols. Please note that symbols like "NO" are not included in the contact point symbols and are just provided for demonstration purposes.

Moujen products revolve around these 3 forms of contact. There is a form Z type that is similar to form C but with a slight difference. Here is the diagram:







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