Emacs and undo with Control + slash

Hello,

I'm doing some development stuff with my newly purchased mac.
I'm working with Emacs and I use the undo shortcut: control+ /
Unfortunately this one is not working on my mac. I know it doesn't come from emacs because I tried to ssh a linux machine where I know I can use control+slash and it didn't worked.
Instead of doing undo, my computer is just ringing a bell.
It should be a default global shortcut of mac OS X but I didn't find it.

Someone has an idea ?

Thanks,
cheers,
Benoit

PS: Please don't tell me I can re-bind the undo key because I have been working all my life with that key binding and don't want to change it now

up !
No one knows how to enable the keyboard combinaison: control + slash ?

up!