I've read the docs, but I'm not clear of the difference between the two. Can anyone shed some light on this please ? Both seems to be called before a system state change. What is the influence of both on the system ? Should I implement both or only one is needed ? Regards Francis _______________________________________________ darwin-kernel mailing list | darwin-kernel@lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.