APEM switch contact configuration

This concerns part IRR1S422L0S. On Digi-Key website it is listed as function: ON - OFF, suggesting normally closed contacts - when the button is pressed in, switch contacts are opened. Is this correct? I don’t see an option for normally closed contacts in the APEM datasheet.
Mouser also lists this particular switch as ON - OFF, also suggesting normally closed contacts. But the datasheet from the manufacturer seems to contradict this.

Would be great if you could clear this up for me!

Welcome to the Digikey tech forum. According to the data sheet this switch should be a OFF-ON function . When in doubt use the information on the manufacturer data sheet.

Thanks! I will have to keep looking for another switch it seems …

I’d kindly suggest that for an SPST latching switch, the concept of “normally open” etc. doesn’t mean much; there’s one set of contacts that toggles state every time the switch is pressed. Like a clicky pen. It’s neither an “on-off” switch, nor an “off-on” switch, it’s an “on-off-on-off-on-off-on-off-on-off-on-off-on-off” switch…

The “switch function” attribute is meant to convey momentary vs sustained positions. If one’s looking to identify normally open vs normally closed or multi-throw contacts, the adjacent “circuit” attribute is better-suited

Hi Oskar.B,

Are you looking for a switch that is normally closed when not pressed, but which opens when pressed and closes again when released? If so this is considered “Normally Closed, Momentarily Open”, which appears in the filters as “On-Mom”. To expand your options, you may want to include “On-Mom, Off-Mom”, which does what you want, but which just has extra switch functions you could ignore.


A starting point of pushbutton switches with such functionality is here.

Thanks, I was a bit hasty and didn’t realise I could filter it that way.

Yes, normally closed, opens when pressed, but … also latching in the pressed state. I have tried a few different searches now and this seems like a rare configuration! Switches that momentarily opens are plentiful though. The easiest solution might be to invert this in the circuit - the switch connects to a pushbutton IC controller.

As Rick states, with a switch which latches, it really doesn’t make a difference whether it is called “On-Off” or “Off-On”, as it will just change states every time it is pressed and released. Therefore, any switch described as either of those listed above, and also including “On-On”, which just means it will have extra unused contacts, should work as needed.

Here’s a link to those.