JETPILOT wrote on Jul 20^th, 2009 at 11:33pm:

I think your inquiring ablut the altitude alert? It's simply an aural warning and visual reminder when climbing or descending to an altitude. It has no autopilot function.

Thanks, it is indeed the altitude alert, I found it in the manual.-
About the AP problem, in your case, does it holds altitude steadily without ups and downs at first ?