# Switches: what does DPST and the like mean?



## Cemoi (Oct 16, 2009)

Looking at catalogues for switches (like e.g. this one), I see DPST, SPST, SPDT and DPDT.
What to these stand for?


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## csshih (Oct 16, 2009)

here ya go: http://www.kpsec.freeuk.com/components/switch.htm#standard

the pictures are very informative


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## Tekno_Cowboy (Oct 16, 2009)

S=Single
D=Dual
P=Pole
T=Throw


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## Cemoi (Oct 16, 2009)

csshih said:


> here ya go: http://www.kpsec.freeuk.com/components/switch.htm#standard


Thanks a lot, very useful link!
Nevertheless when browsing the Mouser pushbutton switches catalogue, I'm still puzzled by many entries in the Contact Form and Switch Function menus:
- DPST NC, SPST NO DB, etc.
- what is the difference (in Switch Function) between ON-OFF and OFF-ON?

Besides trying to better understand all this, I'm trying to find a switch similar to this one (on-off, IP56, fits nicely in a steerer tube end) in the US, so any suggestion would be appreciated.


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## uk_caver (Oct 16, 2009)

For non-locking pushbuttons, 'NO' and 'NC' are 'Normally Open' and 'Normally Closed', showing the normal state (when the button isn't pressed).

A NO switch is normally open, and closes ('makes') the contact when pressed, so could also be called 'push-to-make' or 'momentary on'.

If not specified, NO and NC usually refer to single-pole switches, and might also be called SPNO and SPNC


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## TorchBoy (Oct 18, 2009)

Cemoi said:


> Besides trying to better understand all this, I'm trying to find a switch similar to this one (on-off, IP56, fits nicely in a steerer tube end) in the US, so any suggestion would be appreciated.


You could try http://www.jaycar.com/productView.asp?ID=SP0743.


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