Hi Dieter

> I think the desired function can be achieved by an mixer with
> adjustable followed by an attenuator.

You are right, thats what I am doing now.

> If that's right we speak about a new module which is a reduced A-138c with a
> manually adjustable offet (positive and negative), an input that is added to
> this offset and an output attenuator or polarizer for the sum.

I think an extra output attenuator would not be required, because it is
contained usually already in the modulation destination. But if it was
was done as a polarizer, it would add a welcome additional function.

Florian