A method for controlling knocking in multi-cylinder internal combustion engines in KC emergency operation and at activated guide-cylinder function are provided by which a torque loss is able to be avoided at low application expenditure and the functionality desired by the guide-cylinder function is maintained even in KC emergency operation. In one embodiment, unknown sources are spatially grouped to produce a system interaction matrix with block factors of low rank within a given error tolerance and the unknown sources are determined from compressed forms of the factors. The superimposed image projection unit generates multiple images with identical content but at least partially different brightness and projects a different superimposed image depending on the projection image. The sewing ring may be formed by a suture-permeable annular member surrounded by a fabric covering, the annular member desirably being molded of silicone. This provides a heart activity signal for display which has the appearance and most attributes of a surface EKG.