Tony M Aug 13, 2015:

@ Asker Yes, I think so!

Do just note, though, that 'latching' would not be the correct technical term for this in EN, regardless of what slavish word-for-word translation might lead one to expect.

claude-andrew (asker) Aug 13, 2015:

@Tony Thanks - yes, I think we're there.

Tony M Aug 13, 2015:

@ Asker This EN data sheet (obviosuly translated) referes to it as a 'maintained contact' — although still slightly puzzling, i think this is begiining to make more sense. From other clues in the datasheet, I am beginning to suspect it is more or less as I first thought — the contact is 'maintained' even when the key is taken out; i.e. the key can be removed in BOTH positions — this is a common feature of certain types of key switch (e.g. those found in lift cabins)

I think this ought to help you ask the right question of your customer, just to make sure you have it right!

claude-andrew (asker) Aug 13, 2015:

Maybe ... I think I may have it: latching means you don't have to re-lock it to remove the key, you can remove it when it's unlocked. (Thanks for leading me there Liz)

claude-andrew (asker) Aug 13, 2015:

@Tony Point taken, Tony. I'll put it in my list of questions for the client.

Tony M Aug 13, 2015:

@ Asker Fair enough... but just before accepting what appears to be the obvious solution, do just stop and check how and why a keyswitch would be called 'latching' in EN? Are there any other examples of it from other manufacturers? I remain sceptical as to the technical validity of this term used in this context.

claude-andrew (asker) Aug 13, 2015:

@DLyons and Herbie Thanks a lot for this detective work! Latching it would appear to be.

Herbie Aug 13, 2015:

A look the data sheet in German is surprising, and it seems to clear the matter. "VERR" stands for "Verrastend". DLyons was right with his initial assumption.
Not very kind of the Siemens-people or the specifier of the French text to leave this rather seldom abbreviation unmodified in the FR description...

Tony M Aug 13, 2015:

@ Asker I suppose it is just possible it means 'verrouillable' and is simply there to make it explicit it is a keyswicth, since that is not actually specifically mentioned anywhere else in the description (other than obliquely with the mention of the Ronis keys).

DLyons Aug 13, 2015:

@Tony I haven't thought about this. I'm just reading the data sheet :-)

claude-andrew (asker) Aug 13, 2015:

Thanks to both. Looks like I'm going to have to ask the client.

Tony M Aug 13, 2015:

@ DLyons Although 'latching' would certainly be logical in some contexts, I can't quite see how it would apply here. Some key switches are indeed 'momentary' (think car ignition switch) — but if they are not, then they are just 'normal' switches, and don't need to be specifically described as 'latching' — unless it is a very unusual type, where the key action is momentary, with a srpung return, BUT the actual contacts remain latched till next time the key is operated. I've never personally encountered such a device, and have some trouble imagining what it might be used for?

It is I suppose possible this might in some way (though I can't quite see how) be referring to the fact that the key can be removes in either positions — now this IS a parameter that is often quoted for keyswitches and would certainly make sense, even though it is hard to see how the FR text could actually be intended to mean that.

DLyons Aug 13, 2015:

There's a data sheet for this (or very similar) at
http://www.mercateo.co.uk/p/2811-3SB3000(2d)4ED01/Switch_rot...

It suggests to me that "latching" is what's intended.