Thank you all for your answers. I did not spell out I have a manual, the original paper book and some PDF file versions, but not the one I need. Now I have it, easy down load from Artek media , very good scan for only 12 USD. And all problems are solved with the help of this manual. They changed a lot of things in the 8640B from first release compared to the last. Very good signal generator! 73, Alf