2 input signals are summed proportionately to 0-100% (e.g. in relation 60/40 or 15/85). Which is used, for example, as an expression of the size ratio of fume cupboard air quantities. The resulting signal can then be converted to a desired output voltage. I.e. 3-6V input voltage can be scaled to e.g. 0-10V / 9-10V or 2-4V output voltage. Likewise, 0-10V input voltage can be scaled to e.g. 0-2V or 8-10V output voltage. Manual only in Danish