Daniel Marquis (asker) Dec 10, 2011:

To both of you... ...I will send you a photo which has been sent to me by my client. As you will see, it does not look like a ''common mode choke''. Best regards and thanks again for your help.

Tony M Dec 5, 2011:

@ Daniel Ok, thanks for that explanation Daniel; it's very important when giving context to explain, as it can be very misleading (as in this case!).

The problem is, there is a 3-way ambiguity here in EN; it could be:

1) A choke in the common ground connection (that's what I've attempted to translate in my suggestion below)

2) A choke common to more than one ground connection

3) Or of course, it might just be a 'ground choke' of a 'common' type — though I think this usage of 'common' is less likely, at least, assuming this is otherwise good-quality, native-speaker EN.

Daniel Marquis (asker) Dec 5, 2011:

À Tony No, this is not the ACTUAL device. For the time being, I got only a photo showing a rectangular closed box with 4 pins at the base. There is nothing written on this ''box'' and I just asked more details to my client. I'll tell you when (and if!) I get something more precise.

Tony M Dec 5, 2011:

Context? Once again, Daniel, it is necessary to ask you if the illustration you have posted is in fact the actual device in question — I suspect not, as this seems to be from a Chinese site, which incorrectly describes it as a 'common choke' (I assume they probably mean 'standard choke') — which is totally different from a 'common ground choke'!!!